for me it is end of Feb early March. But with the way the weather is at the moment.......
I was always told March, April & May is spring.

New territory for us this, we have never had as acid a soil as this is. pH of 6.6 on average over the area I tested.

What pH does a lawn prefer then? Our soil is about 6.5 and has never shown any sign of needing lime. (excuse me for butting in )

Our lawn is very mossy and the best way to deal with it is to raise the pH level.

I wish the moss knew this my soil ranges from pH 7.9-8,3 and it still grows merrily. Hubby does need to spike it again, but there is lots of shade which doesn't help.

Our neighbour is the greens keeper for the local Bowling club so he knows a little about grass. He suggested the lime for it as Lawn sand (Ferrous oxide) makes it more acidic. Certainly the lime we put on last year improved the grass no end.
Moss is supposed to grow best on a hungry soil, but our last garden was the most fertile soil we have ever had and it was covered in moss.
This area seems to be very prone to moss. Our roof is covered in it.

Moss flourishes here too, as the climate is so wet. If lime discourages moss that's well worth remembering so thank you!.
Owd, do your local birds love the moss on your roof? Here they collect it for nest lining. Pity a lot of it gets dropped on the path...

What birds? We only get hundreds of pigeons and jackdaws, very little else.
We tried doing the Birdcount thing and got the big fat total of NONE!
No idea why. We put out food and it just went bad as nothing ate it.