Convert local date time to GPS week, seconds of week Google Gadget

Note: A WebApp version of this Google Gadget is available at https://dominoc925-pages.appspot.com/webapp/calc_timegps/

This Google Gadget calculator can convert the local date time values into the equivalent GPS week and seconds of week format. The GPS leap seconds from 1980 till 2012 are taken into account in the conversion now.  This came about since I found that in some situations, I need to find out the equivalent GPS week and seconds of week for a given local date time. So I wrote this gadget to do the job. 

To use this calculator, 

1. Simply select your time zone.
2. Then type in the local date time.
   
   Note: The time should be entered in 24HR form. It is not necessary to fill in all local date time fields - the calculator will use zero values in place of blank fields.
3. Then click the Convert to GPS time button.
   
   If the keyed in local date time values do not represent a valid date time string, then the calculator will simply display an error 'Invalid date time' message. Otherwise, the GPS week and seconds of week values will be shown in the GPS Time field.