Nexus 7 wifi icon showing as full but greyed out

I let my nexus 7 completely run down its battery whilst on holiday and noticed after charging it on my return that I couldn't connect to secure internet sites and that the wifi icon was showing full but greyed out.

Fortunately its really easy to fix.

For some reason the date is lost when completely battery drained and this weirdly affects your t'interweb. Check the date in your settings. It will show something whacky like 1999/2000. Fix the date to the current one, save and it should fix your wifi issues if like mine it was showing as connected but the wifi icon was greyed out.