House of Lords Library

Lengths of Prorogation since 1900

Published Wednesday, September 11, 2019

This House of Lords Library briefing sets out the start and end dates of each parliamentary session since 1900, together with the number of calendar days between the end of the previous session and the start of the new one.

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Prorogation is the mechanism by which parliamentary sessions are ended. On 28 August 2019, it was announced that Parliament would be prorogued no later than 12 September 2019. It was confirmed on 9 September that Parliament would be prorogued later that day, bringing an end to the current 2017­-19 session which started in June 2017. A Royal Commission formally prorogued Parliament on Tuesday 10 September 2019 at 1:40am.

The new parliamentary session is due on 14 October 2019, 33 calendar days after the end of the 2017-19 session. This would constitute the largest number of calendar days between the end of one session and the start of the next since the 1930-31 session (excluding first sessions of new parliaments, ie those following general elections). 

To put the 33 calendar days into context:

  • Between 1900 and 1930, it was not unusual for there to be lengthy breaks between sessions, a mean average of about 72 calendar days. The median average was 53 calendar days.
  • Between 1930 and 2017, the mean average was about 5 calendar days, a median average of about 4 calendar days.
  • Between 1999 and 2017, the mean average was about 8 calendar days. The median average is around 5 calendar days.  

Figures for first sessions of new parliaments (ie those following a general election) are available in the data table below. These will have larger gaps between the end of the previous session and the start of the first of the new parliament, encompassing dissolution and subsequent election periods.  


The calculations provide the number of whole calendar days between the close of each session and the start of the next. Calendar days enable direct comparison across the period considered. This method avoids the need to take into account variation/expectation in sitting patterns, both in terms of when sessions start and end (eg time of year) and the days each House would have expected to sit at that time. The number of calendar days given will also include weekends and bank holidays that fell between any two dates. Additionally, they will include days it might be expected would fall within a periodic adjournment. Adjournments typically include for Easter, summer and Christmas. However, the occasions for adjournment, and the length, will vary depending on the period considered.

Lords Library notes LLN-2019-0111

Author: Matthew Purvis

Topics: Constitution, General elections, House of Commons, House of Lords, Parliament, Parliamentary procedure

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