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Iso8601DurationHelper

A small library to handle ISO8601 durations (e.g. P1Y for 1 year, PT2H30M for 2 hours and 30 minutes) in C#.

Some libraries attempt to parse these durations to TimeSpan, but it doesn't really make sense, because TimeSpan doesn't have a concept of month, so they just translate P1M to 30 days. This is wrong because all months don't have the same number of days; January 1 + 1 month should be February 1, not January 31.

This library introduces a Duration struct with operators to add a duration to or subtract a duration from a date, with the proper semantics. For instance:

var startDate = new DateTime(2018, 1, 1);
var duration = Duration.Parse("P2M");
var endDate = startDate + duration; // 2018/03/01