Earth Day time (5)
I believe the answer is:
april
'earth day time' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for april that I've seen before include "on her first kid" , "Month of showers and of the Queen's birthday" , "Thirty days in spring" , "TS Eliot's 'cruelest month'" , "Month to be in England (Browning)" .)