There are generally 11 public holidays per year, due to the differences between the Islamic calendar and the Gregorian calendar, Hari Raya Aidil Fitri and Hari Aidil Adha are mutually celebrated twice in a Gregorian calendar every 32 or 33 years. This happened in 1968 and 2000 for Hari Raya Puasa as well as 1974 and 2006 for Hari Raya Haji, giving Singaporeans 12 public holidays in those years.
Yearly Calendar 2019 with Singapore Holidays
If any public holiday comes on a Sunday in Singapore, the consecutive day is announced to be a public holiday if it is not itself already a public holiday, since National Day in 2015 landed on a Sunday, two additional holidays were given (on August 7 and August 10).
Singapore Holidays Calendar 2019
The Chief Executive is allow to declare any day to be noticed as a public holiday in addition to or substitution for any day specified in the schedule to the Holidays Act,also announce any day in a year to be noticed as an extra public holiday when in that year two public holidays comes on the same day.
If any public holiday comes on a Saturday in Singapore, the following Monday is declared as a school holiday for students in primary & secondary schools, only if that Monday is not a public holiday itself.