All 26 cantons, with no municipal exception in the existing official overview.
Only Swiss National Day on 1 August has federal constitutional holiday status. Ascension Day applies in every canton through cantonal rules.
Approved leave on Friday, 15 May creates a four-day break; without leave, the normal workplace and school rules apply on Friday.
Legally, 14 May is a public holiday in every canton; that does not make 15 May an automatic day off for employees or schools. Shops and services may use holiday hours on Thursday, while Friday will often return to the normal weekly schedule.
