Kraken Exchange API: AddOrder's expiretm parameter

Does the API AddOrder() command support expiretm for limit orders? I always get an EGeneral:Invalid arguments:expiretm error when I set this parameter.

I tried to expire 3 seconds from now with the following settings:

1) expiretm = 3             # int
2) expiretm = "+3"          # string
3) expiretm = 1500226507    # int

No luck, all return the mentioned error. Only expiretm = 0 is accepted.

• Is expiretm supported for limit orders?
• Which syntax is the right one: (1) or (2)?

Thx