Calendar boy? (6)

I believe the answer is:

julian

I believe this is a double definition.

'calendar' is the first definition.
(Julian calendar is an example)

'boy?' is the second definition.

(Other definitions for julian that I've seen before include "Calendar devised by Caesar" , "Associated with Caesar" , "Sort of date" , "boy" .)

I've seen this clue in the Evening Standard.

Want a hint initially instead of a full solution? Install my app