date of 1st entry vs date entry application is based on

Hi to All,

My wife first arrived to UK on 06/06/2003 but after one month she left for 4 months to give birth for our first child, back to UK on 01/12/2003, question now is that if we calculate her absence since 06/06/2003 she will be over the 540 days threshold, but if we based her application on the next entry 01/12/2003 she will be eligible soon as her days out will be around 500 days with no gaps and no 180 days in a row.

Question D2 of Set (LR) form state:
When did you first enter the UK? this refer to the date of your first entry into the UK at the beginning of the period of stay on which this application is based.

I really need your views on which date to write down as there is only one space for one date.

Best regards
Tsmoussa

If you are counting continuous period from 01/12/2013 then mention the same in the application.