Many developers know about the interchange formats for dates and times defined by ISO 8601. (For example 2007-08-31T16:47+00:00 which represents 16:47 on August 31, 2007 in UTC) However, what is not so well-known (at least in my experience), is that this standard also defines a format for Durations. Here are a few examples: P1Y – 1 ...