Specifying Time-To-Live values.
The following table includes a list of TTL expressions:
Custom expiration syntax examples
Description
30m
Expires after 30 minutes.
24h
Expires after 24 hours.
5d
Expires after 5 days.
1w
Expires after 1 week.
3M
Expires after 3 months (3*30 days).
1y
Expires after 1 year (365 days).
modified +24h
Calculate 24 hours since modification time, and set expiration accordingly.