Fixes for timezone parsing in iCal feeds

[rbrunt]

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Our site was having issues with timezones (daylight saving time) because the event aggregator plugin wasn't normalising timezones, meaning events appeared an hour offset from where they should have done on our site.

I had to apply these fixes to get it working. I haven't tested them exhaustively outside our specific use case, but I don't see why they shouldn't work in general, possibly with a little tweaking.

[iamdharmesh]

Hello @rbrunt,

Thanks for your pull request, I will review it once get time.

Best Regards

[rbrunt]

Hi @iamdharmesh - did you get a chance to look at this? Our site has had issues with imported calendar entries since the clocks changed in the UK a couple of weeks ago.