added date functions to CHANGELOG

CHANGELOG

@@ -1,6 +1,92 @@
 v2.7.0 (XXXX-XX-XX)
 -------------------
 
+* added extra AQL functions for date and time calculation and manipulation. 
+  These functions were contributed by GitHub users @CoDEmanX and @friday. 
+  A big thanks for their work! 
+
+  The following extra date functions are available from 2.7 on:
+
+  * `DATE_DAYOFYEAR(date)`: Returns 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)`: Returns 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)`: Returns whether the year of *date* is a leap year.
+
+  * `DATE_QUARTER(date)`: Returns 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(date)*: Returns the number of days in *date*'s month (28..31).
+    
+  * `DATE_ADD(date, amount, unit)`: Adds *amount* given in *unit* to *date* and
+    returns the calculated date.
+
+    *unit* can be 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
+
+    *amount* is the number of *unit*s to add (positive value) or subtract
+    (negative value).
+
+  * `DATE_SUBTRACT(date, amount, unit)`: Subtracts *amount* given in *unit* from
+    *date* and returns 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_DIFF(date1, date2, unit, asFloat)`: Calculate the difference
+    between two dates in given time *unit*, optionally with decimal places.
+    Returns a negative value if *date1* is greater than *date2*.
+
+  * `DATE_COMPARE(date1, date2, unitRangeStart, unitRangeEnd)`: Compare two
+    partial dates and return true if they 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.
+    Pass the unit to start from as *unitRangeStart*, and the unit to end with as
+    *unitRangeEnd*. All units in between will be compared. Leave out *unitRangeEnd*
+    to only compare *unitRangeStart*.
+
+  * `DATE_FORMAT(date, format)`: Format a date according to the given format string.
+    It supports the following placeholders (case-insensitive):
+    - %t: timestamp
+    - %z: ISO date (0000-00-00T00:00:00.000Z)
+    - %w: day of week (0..6)
+    - %y: year (0000..9999)
+    - %m: month (01..12)
+    - %d: day (01..31)
+    - %h: hour (00..23)
+    - %i: minute (00..59)
+    - %s: second (00..59)
+    - %f: millisecond (000..999)
+    - %x: day of year (001..366)
+    - %k: ISO week date (01..53)
+    - %l: leap year (0 or 1)
+    - %q: quarter (1..4)
+    - %a: days in month (28..31)
+    - %n: English name of month (January..December)
+    - %o: abbreviated English name of month (Jan..Dec)
+    - %e: English name of weekday (Sunday..Saturday)
+    - %g: abbreviated English name of weekday (Sun..Sat)
+    - %%: literal %
+
 * new WAL logfiles and datafiles are now created non-sparse
     
   This prevents SIGBUS signals being raised when memory of a sparse datafile is accessed