* @param timestr a string representing a date or a duration.
* - If a date the syntax is:
* @code
- * [{YYYY-MM-DD|YYYYMMDD}[T|t| ]]{{HH[:MM[:SS[.m...]]]}|{HH[MM[SS[.m...]]]}}[Z]
+ * [{YYYY-MM-DD|YYYYMMDD}[T|t| ]]{{HH:MM:SS[.m...]]]}|{HHMMSS[.m...]]]}}[Z]
* now
* @endcode
* If the value is "now" it takes the current time.
* year-month-day.
* - If a duration the syntax is:
* @code
- * [-]HH[:MM[:SS[.m...]]]
+ * [-]HH:MM:SS[.m...]]]
* [-]S+[.m...]
* @endcode
* @param duration flag which tells how to interpret timestr, if not