13 Datetime Arithmetic

9.0

13Datetime Arithmetic🔗 i

value
gen:datetime-arithmetic-provider :any/c

An interface that defines datetime arithmetic operations. It is implemented by all objects that satisfy datetime? , moment? , or period? .

procedure
( datetime-arithmetic-provider? x)→boolean
x:any/c

Returns #t if x implements gen:datetime-arithmetic-provider ; #f otherwise.

procedure
( +period dtp)→datetime-arithmetic-provider?
dt:datetime-arithmetic-provider?
p:period?

procedure
( -period dtp)→datetime-arithmetic-provider?
dt:datetime-arithmetic-provider?
p:period?

Adds or subtracts p to/from dt, returning a fresh datetime arithmetic provider the same type as dt.

Examples:

> (+period (datetime 1970)(period [years 5][hours 2]))

#<datetime 1975年01月01日T02:00:00>
> (-period (moment 2015383#:tz"America/New_York")(hours 2))

#<moment 2015年03月08日T00:00:00-05:00[America/New_York]>
> (+period (years 10)(years -5))

#<period of 5 years>

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