Day Date Month Holiday
Thursday 12 Jan Duruthu Full Moon Poya Day
Saturday 14 Jan Tamil Thai Pongal Day
Saturday 04 Feb National Day
Friday 10 Feb Navam Full Moon Poya Day
Friday 24 Feb Mahasivarathri Day
Sunday 12 Mar Madin Full Moon Poya Day
Monday 10 Apr Bak Full Moon Poya Day
Wednesday 12 Apr Sinhala and Tamil New Year's Eve
Thursday 13 Apr Sinhala and Tamil New Year's Day
Friday 14 Apr Good Friday
Monday 01 May Labour Day
Wednesday 10 May Vesak Full Moon Poya Day
Thursday 11 May Day after Vesak Full Moon Poya Day
Friday 09 Jun Poson Full Moon Poya Day
Monday 26 Jun Eid-al-Fitr (End of Ramadan)
Saturday 08 Jul Adhi Esala Full Moon Poya Day
Monday 07 Aug Nikini Full Moon Poya Day
Saturday 02 Sep Eid-al-Adha (Feast of Sacrifice)
Tuesday 05 Sep Binara Full Moon Poya Day
Thursday 05 Oct Vap Full Moon Poya Day
Wednesday 18 Oct Deepavali
Friday 03 Nov Il Full Moon Poya Day
Friday 01 Dec Milad-Un-Nabi (Holy Prophet's Birthday)
Sunday 03 Dec Unduvap Full Moon Poya Day
Monday 25 Dec Christmas Day
Source: https://www.timeanddate.com/holidays/sri-lanka/2017#!hol=9