Sick line, 1 month?

[FortyFacedFuckers]

Silly question on Friday I got a sick line from my gp for 1 month, would I be due back at work in 4 weeks or would it be a calendar month?
Thanks in advance, I have never had a sick line before and never thought to check at the time.

One month to me would mean one calendar month. So date in form is eg 8th Dec, you go back to work 8th Jan.

Does it not specify a date it began? If so, it's one calendar month from then.

Thank you, probably over thinking it.
It began on the 7th dec so return on 7th January then.