The first seconds of the new millennium in Co Donegal will be counted in on an old railway station clock, which has been restored and mounted in a specially-designed tower on the main street in Stranorlar.
The last train ever to pull into Stranorlar station arrived at 8.20 p.m. on December 31st, 1959, and the station clock has been held in storage for the past 40 years.
As a millennium project, a local development group teamed up with Donegal County Council to have the clock remounted on the main street.
A Dublin architect, Mr Martin Henchion, came up with the winning design for the new clock tower, a beacon-like stainless steel structure lighting up the surrounding area.
Unveiling celebrations will start at 11 p.m., and an ecumenical service will be held.
Another unusual millennium project will start today at Letterkenny General Hospital, when a local photographer, Ms Ann McMenamin, will take up residence among the patients and staff.
Over three days she will capture the happenings at the hospital, and her pictures will be published in book form, and included in an exhibition next year.
For lovers of traditional music the Frankie Kennedy Winter School has been running as normal this year, from December 28th to January 2nd, in Dunlewy in north Donegal. Established some years ago in honour of the former Altan member who died from cancer, the school includes workshops and concerts. Members of Altan and some friends are taking part.
Some ecumenical church services are planned in Co Donegal. In the Gaeltacht village of Crolly an outdoor "crossroads" service will be held, particularly for returning emigrants, and will include a music session.
The highlight of the celebrations in Sligo will be tomorrow in the grounds of the 12th-century Sligo Abbey. The monastery is being opened specially to stage the Last Lights ceremony, and clergy of various denominations will take part in an ecumenical service.
Music will be provided by the Sligo Early Music Ensemble and local traditional musicians. The ceremony will run from 4 p.m. to 6 p.m. and numbers will be restricted to about 1,000 people. Another lights ceremony will be held in Ballymote Castle tomorrow.
The Co Leitrim Last Lights ceremony will take place in the grounds of the new civic offices in Carrick-on-Shannon from 4.20 p.m. Proceedings will also include ecumenical prayers and the raising of the millennium flag.
A range of church services and musical events are also taking place in both counties.