Julian to Gregorian Calendar in 1752 (UK)

It's likely you will have come across dates where the transcribed year appears in the format 1748/49. The reason for this isn't uncertainty by the transcriber, two years are entered to use both the Julian and Gregorian calendars.

Prior to the UK adopting the Gregorian Calendar in 1752, the year began on 25th March rather than 1st January.   

The relevance of this to genealogists

It's common practice for transcribers to show dates from both the Julian to the Gregorian Calendar. This means that any event prior to 1752 which took place between 1 January (New Year's Day in the current, Gregorian calendar) and 24th March (New Year's Eve in the Julian Calendar) is written using both the Julian and Gregorian year.

For example: 

If a child was born on 25th February 1748, and baptised on 27th March 1749 it can appear that the parents waited over a year for the baptism, when the baptism actually took place when the baby was 4 weeks old (remember, New Year's Day was 25th March). To avoid this confusion, it's common for transcribers to display the birthdate as 25th February 1748/49, which shows the actual year (1748) and the year converted to the Gregorian Calendar (1749). Note that as the baptism took place after the 25th March New Year's Day, there's no need to convert that.