Required. A human readable expression representing the number of seconds to provide.
The format supported is a number followed by an expression. It currently
s second seconds sec secs
m minute minutes min mins
h hr hour hours
d day days
w week weeks
M month months
y year years
Months and years are currently fixed at 30 and 365 days. This may change.
Anything else is used verbatim as the expression of a number of seconds.
2 hours, 3 days, 3d, 1 week, 3600, etc...