The cookies expiration date. There are several formats.
Unix epoch time like 1288817656 to mean Wed, 03-Nov-2010 20:54:16 GMT
A human-readable offset from the current time such as 2 hours. 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.