Tynwald Day is a public holiday on what island?

Tynwald Day (Manx: Laa Tinvaal) is the National Day of the Isle of Man, usually observed on 5 July (if this is a Saturday or Sunday, then on the following Monday).

On this day, the Island's legislature, Tynwald, meets at St John's, instead of its usual meeting place in Douglas. The session is held partly in the Royal Chapel of St John the Baptist and partly in the open air on the adjacent Tynwald Hill (a small artificial mound). The meeting, the first recorded instance of which dates to 1417, is known as Midsummer Court. It is attended by members of the two branches of Tynwald, the House of Keys, and the Legislative Council. The Lieutenant Governor, the representative of the Lord of Mann, presides except on the occasions when the Lord of Mann or another member of the British Royal Family is present.

All bills that have received Royal Assent are promulgated on Tynwald Day. Any Act of Tynwald which is not so promulgated within 18 months of passage ceases to have effect. Other proceedings include the presentation of petitions and the swearing in of certain public officials.