There is usually no set minimum or maximum amount of time set aside for the transition to take place, but often in countries that have adopted the Westminster system the incoming head of government will want two or three weeks to put affairs in order and determine who should get cabinet posts, which itself might require more time especially if recounts involving prospective frontbenchers are in progress.
This is not the case in the United Kingdom itself however, where an opposition leader who wins a clear majority in a general election is expected to assume office as soon as possible, often within 24 hours after the polls close.
In some countries the role is specifically covered by legislation, in others, convention applies before the chosen leader is sworn in.
In the Republic of Ireland, where the prime minister and head of government are officially titled and referred to in both English and Irish as the Taoiseach, the person most expected to succeed to the office is variously described as the presumptive Taoiseach, the Taoiseach-designate, the Taoiseach-in-waiting or more rarely the Taoiseach-elect, with no singular style predominating.
[1] In most jurisdictions where the term is used, becoming prime minister-designate grants no special powers, duties or privileges until an appointment to the office is made.
[12] The Solomon Islands' constitution provides fourteen days between the date of the general election and the selection of the prime minister.
During this period, aspiring candidates for prime minister lobby intensely to acquire the numbers needed to win the contest and form the government.