Sunday 04 Jan Milad-un-Nabi
Sunday 04 Jan Duruthu Full Moon Poya
Thursday 15 Jan Tamil Thai Pongal Day
Tuesday 03 Feb Tamil Thai Pongal Day
Wednesday 04 Feb National Day
Tuesday 17 Feb Maha Shivratri
Thursday 05 Mar Madin Full Moon Poya
Friday 03 Apr Good Friday
Friday 03 Apr Bak Full Moon Poya
Monday 13 Apr Sinhala and Tamil New Year Eve
Tuesday 14 Apr Sinhala and Tamil New Year
Friday 01 May May Day
Sunday 03 May Vesak Full Moon Poya
Tuesday 02 Jun Poson Full Moon Poya
Saturday 18 Jul Idul Fitr
Friday 31 Jul Esala Full Moon Poya
Saturday 29 Aug Nikini Full Moon Poya
Thursday 24 Sep Idul Juha
Sunday 27 Sep Binara Full Moon Poya
Tuesday 27 Oct Vap Full Moon Poya
Tuesday 10 Nov Deepavali
Wednesday 25 Nov Ill Full Moon Poya
Thursday 24 Dec Unduvap Full Moon Poya
Friday 25 Dec Christmas Day
Source: http://www.officeholidays.com/countries/sri_lanka/index.php