On 20 September 2015, President Ram Baran Yadav promulgated Nepal's new constitution, drafted by an elected Constituent Assembly after years of debate. It established Nepal as a secular, federal democratic republic, divided into seven provinces.
In short: Nepal's constitution came into force on 20 September 2015. The day is now celebrated as Constitution Day (Sambidhan Diwas), a public holiday.
Background
The monarchy was abolished in 2008 after the civil war and peace process. A first Constituent Assembly failed to agree a constitution; the second, elected in 2013, completed it, shortly after the earthquakes of 2015.
For visitors
The seven provinces are Koshi, Madhesh, Bagmati, Gandaki, Lumbini, Karnali and Sudurpashchim. You will see the names on maps, permits and road signs.