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Date Functions

C8QL offers functionality to work with dates, but it does not have a special data type for dates (neither does JSON, which is usually used as format to ship data into and out of GDN). Instead, dates in C8QL are represented by either numbers or strings.

All date function operations are done in the Unix time system. Unix time counts all non leap seconds beginning with January 1st 1970 00:00:00.000 UTC, also know as the Unix epoch. A point in time is called timestamp. A timestamp has the same value at every point on earth. The date functions use millisecond precision for timestamps.

Time unit definitions:

  • millisecond: 1/1000 of a second
  • second: one SI second{:target="_blank"}
  • minute: one minute is defined as 60 seconds
  • hour: one hour is defined as 60 minutes
  • day: one day is defined as 24 hours
  • week: one week is defined as 7 days
  • month: one month is defined as 1/12 of a year
  • year: one year is defined as 365.2425 days

All functions that require dates as arguments accept the following input values:

  • numeric timestamps, millisecond precision.

    An example timestamp value is 1399472349522, which translates to 2014-05-07T14:19:09.522Z.

    Valid range: -62167219200000 .. 253402300799999 (inclusive)

  • date time strings in ISO 8601{:target="_blank"} format:

    • YYYY-MM-DDTHH:MM:SS.MMM
    • YYYY-MM-DD HH:MM:SS.MMM
    • YYYY-MM-DD

    Milliseconds (.MMM) are always optional. Two digits for the hours (HH), minutes (MM) and seconds (SS) are mandatory, i.e. zero-padding is required for the values 0 through 9 (e.g. 05 instead of 5). Leading zeroes for the year (YYYY), month (MM) and day (DD) can be left out, but is discouraged.

    A time offset may optionally be added at the end of the string, with the hours and minutes that need to be added or subtracted to the date time value. For example, 2014-05-07T14:19:09+01:00 can be used to specify a one hour offset, and 2014-05-07T14:19:09+07:30 can be specified for seven and half hours offset. Negative offsets are also possible. Alternatively to an offset, a Z can be used to indicate UTC / Zulu time. An example value is 2014-05-07T14:19:09.522Z meaning May 7th 2014, 14:19:09 and 522 milliseconds, UTC / Zulu time. Another example value without time component is 2014-05-07Z.

    Valid range: "0000-01-01T00:00:00.000Z" .. "9999-12-31T23:59:59.999Z" (inclusive)

Any date/time values outside the valid range that are passed into an C8QL date function will make the function return null and trigger a warning for the query, which can optionally be escalated to an error and abort the query. This also applies to operations which produce an invalid value.

DATE_HOUR( 2 * 60 * 60 * 1000 ) // 2
DATE_HOUR("1970-01-01T02:00:00") // 2

You are free to store age determinations of specimens, incomplete or fuzzy dates and the like in different, more appropriate ways of course. C8QL's date functions will most certainly not be of any help for such dates, but you can still use language constructs like SORT (which also supports sorting of arrays) and indexes like skiplists.

Current date and time​

DATE_NOW()​

DATE_NOW() → timestamp

Get the current unix time as numeric timestamp.

  • returns timestamp (number): the current unix time as a timestamp. The return value has millisecond precision. To convert the return value to seconds, divide it by 1000.
note

This function is evaluated on every invocation and may return different values when invoked multiple times in the same query. Assign it to a variable to use the exact same timestamp multiple times.

Conversion​

DATE_TIMESTAMP() and DATE_ISO8601() can be used to convert ISO 8601 date time strings to numeric timestamps and numeric timestamps to ISO 8601 date time strings.

Both also support individual date components as separate function arguments, in the following order:

  • year
  • month
  • day
  • hour
  • minute
  • second
  • millisecond

All components following day are optional and can be omitted. Note that no time offset can be specified when using separate date components, and UTC / Zulu time will be used.

The following calls to DATE_TIMESTAMP() are equivalent and will all return 1399472349522:

DATE_TIMESTAMP("2014-05-07T14:19:09.522")
DATE_TIMESTAMP("2014-05-07T14:19:09.522Z")
DATE_TIMESTAMP("2014-05-07 14:19:09.522")
DATE_TIMESTAMP("2014-05-07 14:19:09.522Z")
DATE_TIMESTAMP(2014, 5, 7, 14, 19, 9, 522)
DATE_TIMESTAMP(1399472349522)

The same is true for calls to DATE_ISO8601() that also accepts variable input formats:

DATE_ISO8601("2014-05-07T14:19:09.522Z")
DATE_ISO8601("2014-05-07 14:19:09.522Z")
DATE_ISO8601(2014, 5, 7, 14, 19, 9, 522)
DATE_ISO8601(1399472349522)

The above functions are all equivalent and will return "2014-05-07T14:19:09.522Z".

DATE_ISO8601()​

DATE_ISO8601(date) → dateString

Return an ISO 8601 date time string from date. The date time string will always use UTC / Zulu time, indicated by the Z at its end.

  • date (number|string): numeric timestamp or ISO 8601 date time string
  • returns dateString: date and time expressed according to ISO 8601, in Zulu time

DATE_ISO8601(year, month, day, hour, minute, second, millisecond) → dateString

Return a ISO 8601 date time string from date, but allows to specify the individual date components separately. All parameters after day are optional.

  • year (number): typically in the range 0..9999, e.g. 2017
  • month (number): 1..12 for January through December
  • day (number): 1..31 (upper bound depends on number of days in month)
  • hour (number, optional): 0..23
  • minute (number, optional): 0..59
  • second (number, optional): 0..59
  • milliseconds (number, optional): 0..999
  • returns dateString: date and time expressed according to ISO 8601, in Zulu time

DATE_TIMESTAMP()​

DATE_TIMESTAMP(date) → timestamp

Create a timestamp value from date. The return value has millisecond precision. To convert the return value to seconds, divide it by 1000.

  • date (number|string): numeric timestamp or ISO 8601 date time string
  • returns timestamp (number): numeric timestamp

DATE_TIMESTAMP(year, month, day, hour, minute, second, millisecond) → timestamp

Create a timestamp value, but allows to specify the individual date components separately. All parameters after day are optional.

  • year (number): typically in the range 0..9999, e.g. 2017
  • month (number): 1..12 for January through December
  • day (number): 1..31 (upper bound depends on number of days in month)
  • hour (number, optional): 0..23
  • minute (number, optional): 0..59
  • second (number, optional): 0..59
  • milliseconds (number, optional): 0..999
  • returns timestamp (number): numeric timestamp

Negative values are not allowed, result in null and cause a warning. Values greater than the upper range bound overflow to the larger components (e.g. an hour of 26 is automatically turned into an additional day and two hours):

DATE_TIMESTAMP(2016, 12, -1) // returns null and issues a warning
DATE_TIMESTAMP(2016, 2, 32) // returns 1456963200000, which is March 3rd, 2016
DATE_TIMESTAMP(1970, 1, 1, 26) // returns 93600000, which is January 2nd, 1970, at 2 a.m.

IS_DATESTRING()​

IS_DATESTRING(value) → bool

Check if an arbitrary string is suitable for interpretation as date time string.

  • value (string): an arbitrary string
  • returns bool (bool): true if value is a string that can be used in a date function. This includes partial dates such as 2015 or 2015-10 and strings containing invalid dates such as 2015-02-31. The function will return false for all non-string values, even if some of them may be usable in date functions.

Processing​

DATE_DAYOFWEEK()​

DATE_DAYOFWEEK(date) → weekdayNumber

Return the weekday number of date.

  • date (number|string): numeric timestamp or ISO 8601 date time string
  • returns weekdayNumber (number): 0..6 as follows:
    • 0 – Sunday
    • 1 – Monday
    • 2 – Tuesday
    • 3 – Wednesday
    • 4 – Thursday
    • 5 – Friday
    • 6 – Saturday

DATE_YEAR()​

DATE_YEAR(date) → year

Return the year of date.

  • date (number|string): numeric timestamp or ISO 8601 date time string
  • returns year (number): the year part of date as a number

DATE_MONTH()​

DATE_MONTH(date) → month

Return the month of date.

  • date (number|string): numeric timestamp or ISO 8601 date time string
  • returns month (number): the month part of date as a number

DATE_DAY()​

DATE_DAY(date) → day

Return the day of date.

  • date (number|string): numeric timestamp or ISO 8601 date time string
  • returns day (number): the day part of date as a number

DATE_HOUR()​

Return the hour of date.

DATE_HOUR(date) → hour

  • date (number|string): numeric timestamp or ISO 8601 date time string
  • returns hour (number): the hour part of date as a number

DATE_MINUTE()​

DATE_MINUTE(date) → minute

Return the minute of date.

  • date (number|string): numeric timestamp or ISO 8601 date time string
  • returns minute (number): the minute part of date as a number

DATE_SECOND()​

DATE_SECOND(date) → second

Return the second of date.

  • date (number|string): numeric timestamp or ISO 8601 date time string
  • returns second (number): the seconds part of date as a number

DATE_MILLISECOND()​

DATE_MILLISECOND(date) → millisecond

  • date (number|string): numeric timestamp or ISO 8601 date time string
  • returns millisecond (number): the milliseconds part of date as a number

DATE_DAYOFYEAR()​

DATE_DAYOFYEAR(date) → dayOfYear

Return the day of year of date.

  • date (number|string): numeric timestamp or ISO 8601 date time string
  • returns dayOfYear (number): the day of year number of date. The return values range from 1 to 365, or 366 in a leap year respectively.

DATE_ISOWEEK()​

DATE_ISOWEEK(date) → weekDate

Return the week date of date according to ISO 8601.

  • date (number|string): numeric timestamp or ISO 8601 date time string
  • returns weekDate (number): the ISO week date of date. The return values range from 1 to 53. Monday is considered the first day of the week. There are no fractional weeks, thus the last days in December may belong to the first week of the next year, and the first days in January may be part of the previous year's last week.

DATE_LEAPYEAR()​

DATE_LEAPYEAR(date) → leapYear

Return whether date is in a leap year.

  • date (number|string): numeric timestamp or ISO 8601 date time string
  • returns leapYear (bool): true if date is in a leap year, false otherwise

DATE_QUARTER()​

DATE_QUARTER(date) → quarter

Return which quarter date belongs to.

  • date (number|string): numeric timestamp or ISO 8601 date time string
  • returns quarter (number): the quarter of the given date (1-based):
    • 1 – January, February, March
    • 2 – April, May, June
    • 3 – July, August, September
    • 4 – October, November, December

DATE_DAYS_IN_MONTH()​

Return the number of days in the month of date.

DATE_DAYS_IN_MONTH(date) → daysInMonth

  • date (number|string): numeric timestamp or ISO 8601 date time string
  • returns daysInMonth (number): the number of days in date's month (28..31)

DATE_TRUNC()​

DATE_TRUNC(date, unit) → isoDate

Truncates the given date after unit and returns the modified date.

  • date (number|string): numeric timestamp or ISO 8601 date time string
  • unit (string): either of the following to specify the time unit (case-insensitive):
    • y, year, years
    • m, month, months
    • d, day, days
    • h, hour, hours
    • i, minute, minutes
    • s, second, seconds
    • f, millisecond, milliseconds
  • returns isoDate (string): the truncated ISO 8601 date time string
DATE_TRUNC('2017-02-03', 'month') // 2017-02-01T00:00:00.000Z
DATE_TRUNC('2017-02-03 04:05:06', 'hours') // 2017-02-03 04:00:00.000Z
    RETURN MERGE(
      FOR doc IN @data
        COLLECT q = DATE_TRUNC(doc.date, "year") INTO bucket
        RETURN { [DATE_YEAR(q)]: bucket[*].doc.value }
    )
    @BV {
    "data": [
      { "date": "2018-03-05", "value": "Spring" },
      { "date": "2018-07-11", "value": "Summer" },
      { "date": "2018-10-26", "value": "Autumn" },
      { "date": "2019-01-09", "value": "Winter" },
      { "date": "2019-04-02", "value": "Spring" }
    ]
    }

DATE_ROUND()​

DATE_ROUND(date, amount, unit) → isoDate

Bin a date/time into a set of equal-distance buckets, to be used for grouping.

  • date (string|number): a date string or timestamp
  • amount (number): number of _unit_s. Must be a positive integer value.
  • unit (string): either of the following to specify the time unit (case-insensitive):
    • d, day, days
    • h, hour, hours
    • i, minute, minutes
    • s, second, seconds
    • f, millisecond, milliseconds
  • returns isoDate (string): the rounded ISO 8601 date time string
DATE_ROUND('2000-04-28T11:11:11.111Z', 1, 'day') // 2000-04-28T00:00:00.000Z
DATE_ROUND('2000-04-10T11:39:29Z', 15, 'minutes') // 2000-04-10T11:30:00.000Z
    FOR doc IN @sensorData
      COLLECT
        date = DATE_ROUND(doc.timestamp, 5, "minutes")
      AGGREGATE
        count = COUNT(1),
        avg = AVG(doc.temp),
        min = MIN(doc.temp),
        max = MAX(doc.temp)
      RETURN { date, count, avg, min, max }
    @BV {
    "sensorData": [
      { "timestamp": "2019-12-04T21:17:52.583Z", "temp": 20.6 },
      { "timestamp": "2019-12-04T21:19:53.516Z", "temp": 20.2 },
      { "timestamp": "2019-12-04T21:21:53.610Z", "temp": 19.9 },
      { "timestamp": "2019-12-04T21:23:52.522Z", "temp": 19.8 },
      { "timestamp": "2019-12-04T21:25:52.988Z", "temp": 19.8 },
      { "timestamp": "2019-12-04T21:27:54.005Z", "temp": 19.7 }
    ]
    }

DATE_FORMAT()​

DATE_FORMAT(date, format) → str

Format a date according to the given format string.

  • date (string|number): a date string or timestamp
  • format (string): a format string, see below
  • returns str (string): a formatted date string

format supports the following placeholders (case-insensitive):

  • %t – timestamp, in milliseconds since midnight 1970-01-01
  • %z – ISO date (0000-00-00T00:00:00.000Z)
  • %w – day of week (0..6)
  • %y – year (0..9999)
  • %yy – year (00..99), abbreviated (last two digits)
  • %yyyy – year (0000..9999), padded to length of 4
  • %yyyyyy – year (-009999 .. +009999), with sign prefix and padded to length of 6
  • %m – month (1..12)
  • %mm – month (01..12), padded to length of 2
  • %d – day (1..31)
  • %dd – day (01..31), padded to length of 2
  • %h – hour (0..23)
  • %hh – hour (00..23), padded to length of 2
  • %i – minute (0..59)
  • %ii – minute (00..59), padded to length of 2
  • %s – second (0..59)
  • %ss – second (00..59), padded to length of 2
  • %f – millisecond (0..999)
  • %fff – millisecond (000..999), padded to length of 3
  • %x – day of year (1..366)
  • %xxx – day of year (001..366), padded to length of 3
  • %k – ISO week date (1..53)
  • %kk – ISO week date (01..53), padded to length of 2
  • %l – leap year (0 or 1)
  • %q – quarter (1..4)
  • %a – days in month (28..31)
  • %mmm – abbreviated English name of month (Jan..Dec)
  • %mmmm – English name of month (January..December)
  • %www – abbreviated English name of weekday (Sun..Sat)
  • %wwww – English name of weekday (Sunday..Saturday)
  • %& – special escape sequence for rare occasions
  • %% – literal %
  • % – ignored

%yyyy does not enforce a length of 4 for years before 0 and past 9999. The same format as for %yyyyyy will be used instead. %yy preserves the sign for negative years and may thus return 3 characters in total.

Single % characters will be ignored. Use %% for a literal %. To resolve ambiguities like in %mmonth (unpadded month number + the string "month") between %mm + "onth" and %m + "month", use the escape sequence %&: %m%&month.

note

DATE_FORMAT() is a rather costly operation and may not be suitable for large datasets (like over 1 million dates). If possible, avoid formatting dates on server-side and leave it up to the client to do so. This function should only be used for special date comparisons or to store the formatted dates in the database. For better performance, use the primitive DATE_*() functions together with CONCAT() if possible.

Examples:

DATE_FORMAT(DATE_NOW(), "%q/%yyyy") // quarter and year (e.g. "3/2015")
DATE_FORMAT(DATE_NOW(), "%dd.%mm.%yyyy %hh:%ii:%ss,%fff") // e.g. "18.09.2015 15:30:49,374"
DATE_FORMAT("1969", "Summer of '%yy") // "Summer of '69"
DATE_FORMAT("2016", "%%l = %l") // "%l = 1" (2016 is a leap year)
DATE_FORMAT("2016-03-01", "%xxx%") // "063", trailing % ignored

Comparison and calculation​

DATE_ADD()​

DATE_ADD(date, amount, unit) → isoDate

Add amount given in unit to date and return the calculated date.

  • date (number|string): numeric timestamp or ISO 8601 date time string
  • amount (number|string): number of _unit_s to add (positive value) or subtract (negative value). It is recommended to use positive values only, and use DATE_SUBTRACT() for subtractions instead.
  • unit (string): either of the following to specify the time unit to add or subtract (case-insensitive):
    • y, year, years
    • m, month, months
    • w, week, weeks
    • d, day, days
    • h, hour, hours
    • i, minute, minutes
    • s, second, seconds
    • f, millisecond, milliseconds
  • returns isoDate (string): the calculated ISO 8601 date time string
DATE_ADD(DATE_NOW(), -1, "day") // yesterday; also see DATE_SUBTRACT()
DATE_ADD(DATE_NOW(), 3, "months") // in three months
DATE_ADD(DATE_ADD("2015-04-01", 5, "years"), 1, "month") // May 1st 2020
DATE_ADD("2015-04-01", 12*5 + 1, "months") // also May 1st 2020
DATE_ADD(DATE_TIMESTAMP(DATE_YEAR(DATE_NOW()), 12, 24), -4, "years") // Christmas four years ago
DATE_ADD(DATE_ADD("2016-02", "month", 1), -1, "day") // last day of February (29th, because 2016 is a leap year!)

DATE_ADD(date, isoDuration) → isoDate

You may also pass an ISO duration string as amount and leave out unit.

  • date (number|string): numeric timestamp or ISO 8601 date time string
  • isoDuration (string): an ISO 8601 duration string to add to date, see below
  • returns isoDate (string): the calculated ISO 8601 date time string

The format is P_Y_M_W_DT_H_M_._S, where underscores stand for digits and letters for time intervals - except for the separators P (period) and T (time).

The meaning of the other letters are:

  • Y – years
  • M – months (if before T)
  • W – weeks
  • D – days
  • H – hours
  • M – minutes (if after T)
  • S – seconds (optionally with 3 decimal places for milliseconds)

The string must be prefixed by a P. A separating T is only required if H, M and/or S are specified. You only need to specify the needed pairs of letters and numbers.

DATE_ADD(DATE_NOW(), "P1Y") // add 1 year
DATE_ADD(DATE_NOW(), "P3M2W") // add 3 months and 2 weeks
DATE_ADD(DATE_NOW(), "P5DT26H") // add 5 days and 26 hours (=6 days and 2 hours)
DATE_ADD("2000-01-01", "PT4H") // add 4 hours
DATE_ADD("2000-01-01", "PT30M44.4S" // add 30 minutes, 44 seconds and 400 ms
DATE_ADD("2000-01-01", "P1Y2M3W4DT5H6M7.89S" // add a bit of everything

DATE_SUBTRACT()​

DATE_SUBTRACT(date, amount, unit) → isoDate

Subtract amount given in unit from date and return the calculated date.

It works the same as DATE_ADD(), except that it subtracts. It is equivalent to calling DATE_ADD() with a negative amount, except that DATE_SUBTRACT() can also subtract ISO durations. Note that negative ISO durations are not supported (i.e. starting with -P, like -P1Y).

  • date (number|string): numeric timestamp or ISO 8601 date time string
  • amount (number|string): number of _unit_s to subtract (positive value) or add (negative value). It is recommended to use positive values only, and use DATE_ADD() for additions instead.
  • unit (string): either of the following to specify the time unit to add or subtract (case-insensitive):
    • y, year, years
    • m, month, months
    • w, week, weeks
    • d, day, days
    • h, hour, hours
    • i, minute, minutes
    • s, second, seconds
    • f, millisecond, milliseconds
  • returns isoDate (string): the calculated ISO 8601 date time string

DATE_SUBTRACT(date, isoDuration) → isoDate

You may also pass an ISO duration string as amount and leave out unit.

  • date (number|string): numeric timestamp or ISO 8601 date time string
  • isoDuration (string): an ISO 8601 duration string to subtract from date, see below
  • returns isoDate (string): the calculated ISO 8601 date time string

The format is P_Y_M_W_DT_H_M_._S, where underscores stand for digits and letters for time intervals - except for the separators P (period) and T (time). The meaning of the other letters are:

  • Y – years
  • M – months (if before T)
  • W – weeks
  • D – days
  • H – hours
  • M – minutes (if after T)
  • S – seconds (optionally with 3 decimal places for milliseconds)

The string must be prefixed by a P. A separating T is only required if H, M and/or S are specified. You only need to specify the needed pairs of letters and numbers.

DATE_SUBTRACT(DATE_NOW(), 1, "day") // yesterday
DATE_SUBTRACT(DATE_TIMESTAMP(DATE_YEAR(DATE_NOW()), 12, 24), 4, "years") // Christmas four years ago
DATE_SUBTRACT(DATE_ADD("2016-02", "month", 1), 1, "day") // last day of February (29th, because 2016 is a leap year!)
DATE_SUBTRACT(DATE_NOW(), "P4D") // four days ago
DATE_SUBTRACT(DATE_NOW(), "PT1H3M") // 1 hour and 30 minutes ago

DATE_DIFF()​

DATE_DIFF(date1, date2, unit, asFloat) → diff

Calculate the difference between two dates in given time unit, optionally with decimal places.

  • date1 (number|string): numeric timestamp or ISO 8601 date time string
  • date2 (number|string): numeric timestamp or ISO 8601 date time string
  • unit (string): either of the following to specify the time unit to return the difference in (case-insensitive):
    • y, year, years
    • m, month, months
    • w, week, weeks
    • d, day, days
    • h, hour, hours
    • i, minute, minutes
    • s, second, seconds
    • f, millisecond, milliseconds
  • asFloat (boolean, optional): if set to true, decimal places will be preserved in the result. The default is false and an integer is returned. - returns diff (number): the calculated difference as number in unit. The value will be negative if date2 is before date1.

DATE_COMPARE()​

DATE_COMPARE(date1, date2, unitRangeStart, unitRangeEnd) → bool

Check if two partial dates match.

  • date1 (number|string): numeric timestamp or ISO 8601 date time string
  • date2 (number|string): numeric timestamp or ISO 8601 date time string
  • unitRangeStart (string): unit to start from, see below
  • unitRangeEnd (string, optional): unit to end with, leave out to only compare the component as specified by unitRangeStart. An error is raised if unitRangeEnd is a unit before unitRangeStart.
  • returns bool (bool): true if the dates match, false otherwise

The parts to compare are defined by a range of time units. The full range is: years, months, days, hours, minutes, seconds, milliseconds (in this order).

All components of date1 and date2 as specified by the range will be compared. You can refer to the units as:

  • y, year, years
  • m, month, months
  • d, day, days
  • h, hour, hours
  • i, minute, minutes
  • s, second, seconds
  • f, millisecond, milliseconds
// Compare months and days, true on birthdays if you're born on 4th of April
DATE_COMPARE("1985-04-04", DATE_NOW(), "months", "days")

// Will only match on one day if the current year is a leap year!
// You may want to add or subtract one day from date1 to match every year.
DATE_COMPARE("1984-02-29", DATE_NOW(), "months", "days")

// compare years, months and days (true, because it's the same day)
DATE_COMPARE("2001-01-01T15:30:45.678Z", "2001-01-01T08:08:08.008Z", "years", "days")

You can directly compare ISO date strings if you want to find dates before or after a certain date, or in between two dates (>=, >, <, <=). No special date function is required. Equality tests (== and !=) will only match the exact same date and time however. You may use SUBSTRING() to compare partial date strings, DATE_COMPARE() is basically a convenience function for that. However, neither is really required to limit a search to a certain day as demonstrated here:

FOR doc IN coll
    FILTER doc.date >= "2015-05-15" AND doc.date < "2015-05-16"
    RETURN doc

Every ISO date on that day is greater than or equal to 2015-05-15 in a string comparison (e.g. 2015-05-15T11:30:00.000Z). Dates before 2015-05-15 are smaller and therefore filtered out by the first condition. Every date past 2015-05-15 is greater than this date in a string comparison, and therefore filtered out by the second condition. The result is that the time components in the dates you compare with are "ignored". The query will return every document with date ranging from 2015-05-15T00:00:00.000Z to 2015-05-15T23:99:99.999Z. It would also include 2015-05-15T24:00:00.000Z, but that date is actually 2015-05-16T00:00:00.000Z and can only occur if inserted manually (you may want to pass dates through DATE_ISO8601() to ensure a correct date representation).

Leap days in leap years (29th of February) must be always handled manually, if you require so (e.g. birthday checks):

LET today = DATE_NOW()
LET noLeapYear = NOT DATE_LEAPYEAR(today)

FOR user IN users
    LET birthday = noLeapYear AND
                   DATE_MONTH(user.birthday) == 2 AND
                   DATE_DAY(user.birthday) == 29
                   ? DATE_SUBTRACT(user.birthday, 1, "day") /* treat like 28th in non-leap years */
                   : user.birthday
    FILTER DATE_COMPARE(today, birthday, "month", "day")
    /* includes leaplings on the 28th of February in non-leap years,
     * but excludes them in leap years which do have a 29th February.
     * Replace DATE_SUBTRACT() by DATE_ADD() to include them on the 1st of March
     * in non-leap years instead (depends on local jurisdiction).
     */
    RETURN user

Working with dates and indices​

There are two recommended ways to store timestamps in GDN:

  • string: UTC timestamp with ISO 8601{:target="_blank"}
  • number: unix timestamp{:target="_blank"} with millisecond precision

The sort order of both is identical due to the sort properties of ISO date strings. You can't mix both types, numbers and strings, in a single attribute however.

You can use skiplist indices with both date types. When chosing string representations, you can work with string comparisons (less than, greater than etc.) to express time ranges in your queries while still utilizing skiplist indices:

    db._create("exampleTime");
    var timestamps = ["2014-05-07T14:19:09.522","2014-05-07T21:19:09.522","2014-05-08T04:19:09.522","2014-05-08T11:19:09.522","2014-05-08T18:19:09.522"];
    for (i = 0; i < 5; i++) db.exampleTime.save({value:i, ts: timestamps[i]})
    db._query("FOR d IN exampleTime FILTER d.ts > '2014-05-07T14:19:09.522' and d.ts < '2014-05-08T18:19:09.522' RETURN d").toArray()
    ~addIgnoreCollection("example")
    ~db._drop("exampleTime")

The first and the last timestamp in the array are excluded from the result by the FILTER.

Limitations​

Note that dates before the year 1583 aren't allowed by the ISO 8601{:target="_blank"} standard by default, because they lie before the official introduction of the Gregorian calendar and may thus be incorrect or invalid. All C8QL date functions apply the same rules to every date according to the Gregorian calendar system, even if inappropriate. That does not constitute a problem, unless you deal with dates prior to 1583 and especially years before Christ. The standard allows negative years, but requires special treatment of positive years too, if negative years are used (e.g. +002015-05-15 and -000753-01-01). This is rarely used however, and C8QL does not use the 7-character version for years between 0 and 9999 in ISO strings. Keep in mind that they can't be properly compared to dates outside that range. Sorting of negative dates does not result in a meaningful order, with years longer ago last, but months, days and the time components in otherwise correct order.

Leap seconds are ignored, just as they are in JavaScript as per ECMAScript Language Specifications{:target="_blank"}.