- the string may contain: NNN d NNN h NNN m NNN s
- This represents NNN days, NNN hours, NNN minutes and NNN seconds.
- The embeded white space is optional.
+ the string may contain: NNN Y NNN M NNN W NNN d NNN h NNN m NNN s
+ This represents NNN years, NNN months, NNN weeks, NNN days, NNN hours,
+ NNN minutes and NNN seconds.
+ The embedded white space is optional.