Period

# Module Period

    module Period: sig .. end

A period represents the time passed between two events (a date, a time...). Only an interface defining arithmetic operations on periods is defined here. An implementation of this interface depends on the kind of an event (see module `Time.Period`, `Date.Period` and `Calendar.Period`).

    type date_field = [ `Day | `Month | `Week | `Year ]

    module type S = sig .. end

Common interface for all periods.