and if you're still not thinking this is fun, here's a quote from Wikipedia "But keep in mind that "PT36H" is not the same as "P1DT12H" when switching from or to Daylight saving time."
Maybe surprising for days (could also happen with minutes because of leap seconds technically :-) but for months and years this is more apparent due to month ends and leap years.
oh, you can use commas too.
and if you're still not thinking this is fun, here's a quote from Wikipedia "But keep in mind that "PT36H" is not the same as "P1DT12H" when switching from or to Daylight saving time."
just add a unit to your period parameters. sigh.