I miss some function which would tell me if year is leap. Did I miss something or it is really missing?

There's no direct way so far, but you can construct the dates Mar 1 and Feb 1 of that year, find the number of days between them and decide whether the year is leap based on that number. What is your use case, though?

I have a date and I want to know number of days in that month. date.month.length() requires to pass that boolean.

In that case you can construct the first day of that month, add one month to it, and then find the number of days between these two dates:

val d1 = LocalDate(date.year, date.month, 1)
val d2 = d1.plus(1, DateTimeUnit.MONTH)
val days = d1.until(d2, DateTimeUnit.DAY)

Thanks, I did it somehow similarly (also restructured the code to not need it directly this way). But the main issue here IMO the current API which asks for something I don't have. Either I'd like a) to not provide the isYearLeap. (

date.month.length

) (I know, it's enum, so maybe something like

date.monthLength

). b) or provide easily (

date.month.length(date.isYearLeap)

or

date.month.length(isYearLeap(date))

)