# Date-Time Concepts - 計算

Calculation Documentation

## Timepoints

このセクションでは，GDTL timepoints で行える基本的な算術規則をいくつか示す。

Timepoint + Duration --> Timepoint
Timepoint - Duration --> Timepoint

Duration + Timepoint --> Undefined
Duration - Timepoint --> Undefined

Timepoint + Timepoint --> Undefined
Timepoint - Timepoint --> Duration

## Durations

このセクションでは時間長(time duration)に関する標準的な演算を示す。

Duration + Duration  --> Duration
Duration - Duration  --> Duration

Duration * Integer   --> Duration
Integer  * Duration  --> Duration

Duration() * Integer --> Duration()
Duration()/Integer   --> Duration()

## Intervals

ここに時間間隔(intervals)によって支援された"演算"がある。 それらは半開区間に基づいている。

//These can be defined by either of 2 Timepoints or a Timepoint and Duration
Timeinterval intersects Timeinterval --> bool
Timeinterval intersection Timeinterval --> Timeperiod //results undefined if no intersection
Timeinterval contains  Timepoint    --> bool
Timeinterval contains  Timeinterval --> bool
Timeinterval shift Duration         --> shift start and end by duration amount