In general holiday dates in Latvia do not change, except Easter, and are as follows:

New Year's Day 1 January
Easter  
Labour Day, Convocation of the Constituent Assembly of the Republic of Latvia 1 May
Declaration of Independence of the Republic of Latvia 4 May
Midsummer Day 23 June
St. John's Day 24 June
Proclamation of the Republic of Latvia 18 November
Christmas 24-26 December
New Year's Eve 31 December

 

Changes in 2018

Easter - 30 March and 2 April
 
21 April - working day
30 April - holiday
 
9 July - holiday
 
19 November - holiday