BELFAST
PRONI
The Public Record Office of Northern Ireland will close at 4:45pm on Friday 22 December and re-open at 10am on Thursday 28 December. It will also be closed on Monday 1 January 2018, re-opening at 10am on Tuesday 2 January. (Note: the usual Thursday late nights will not resume until 11 January.)
NIFHS
Usually open on Tuesday afternoons, the North of Ireland Family History Society's Research Centre in Newtownabbey will be closed on 26 December and 2 January. Next opening will be 2pm–8pm on Tuesday 9 January.
DUBLIN
RCB Library
The Representative Church Body Library in Churchtown will close at 1pm on Friday 22 December and re–open to the usual schedule at 9:30am on Tuesday 2 January 2018.
National Library of Ireland
All NLI reading rooms (and the free Genealogy Advisory Service) will be closed from Saturday 23 December to Monday 1 January 2018 inclusive. NLI exhibitions will be open 10am to 4:45pm daily from Wednesday 27 December to Friday 29 December inclusive, and closed from Saturday 30 December to Monday 1 January 2018 inclusive. Normal hours resume at all NLI sites on Tuesday 2 January.
National Archives of Ireland
The Reading Room (and the free Genealogy Advisory Service) will be closed to the public from 12:30pm on Friday 22 December and re-open at 9:15am on Tuesday 2 January 2018.
Military Archives
The Reading Room at the Military Archives closed for the festive season on Tuesday 19 December. It will reopen for appointments on Thursday 4 January 2018.
Dublin City Library & Archive
The DCL&A will be closed from Saturday 23 December to Monday 1 January 2018, inclusive. It will re-open on Tuesday 2 January.
LONDON
The National Archives UK
The UK National Archives will be closed from Saturday 23 December to Wednesday 27 December inclusive, and open for regular hours on Thursday 28 and Friday 29 December. It will also be closed from Saturday 30 December to Monday 1 January inclusive, reopening at 9am on Tuesday 2 January.
Society of Genealogists
For its Christmas break, the Society will be closed from 6pm on Thursday 21 December until 9am on Wednesday 27 December. It will be open for regular hours 27-30 December. As the New Year break will be immediately followed by the SOG's annual stocktaking, the library will be closed from 6pm on Saturday 30 December until 10am on Tuesday 9 January 2018.
IGRS Library
Based at the Society of Genealogists (see above), the library of the Irish Genealogical Research Society is closed until 1:30pm on Saturday 13 January.