you should apply when the weeds are growing from spring till early autumn

Preferably, never. Glyphosate isn't as safe as Monsanto claim!
Read this article:
http://www.i-sis.org.uk/GHCCBD.php
where it suggests birth defects, and the fact that Argentina is considering a ban.

Personally, I make a distinction between spraying it on paths and drives well away from important plants and definitely nowhere near edible crops.

well thats sorted that out thanx for that bertie though i dont get weeds anymore its still worth knowing .