Hijri month are 30 days at max
Results geting from the php functions jdtogregorian and gregoriantojd are not compatible with other calculations
Arguments $month and $day are not optional in the convert_to_gregorian function
bug fix: wrong arguments order when calling get_next_month
changed get_weekdays' implementation to read week days' short name from language file
improved get_starting_weekday's implementation to read the starting week day from configuration or from the user's preferences
just some changes in the comments
change in timestamp_to_date_string to consider languages that do not have upper and lower case letters in their alphabet
pass the second parameter to get_string to read the 'strftimedaydatetime' language string from the file 'langconfig'
comments improvement
MDL-41664
fix for MDL-42537