Timestamp pattern

Let’s assume I have the following timestamp 

local reminder\_timestamp = "2013-12-13T00:00:00+01:00"

And I’m using the below function to return time UTC

 function makeTimeStamp(dateString) local pattern = "(%d+)%-(%d+)%-(%d+)%a(%d+)%:(%d+)%:([%d%.]+)([Z%p])(%d%d)%:?(%d%d)" local year, month, day, hour, minute, seconds, tzoffset, offsethour, offsetmin = dateString:match(pattern) local timestamp = os.time( {year=year, month=month, day=day, hour=hour, min=minute, sec=seconds} ) local offset = 0 if ( tzoffset ) then if ( tzoffset == "+" or tzoffset == "-" ) then -- we have a timezone! offset = offsethour \* 60 + offsetmin if ( tzoffset == "-" ) then offset = offset \* -1 end timestamp = timestamp + offset end end return timestamp end

What should be the pattern above to match the the timestamp I mentioned earlier?

Thank you,

Mustafa