The last time October 25 fell on a Sunday was in 2009.
2016 and then 2022.
In 2009 the UK will change their clocks one hour ahead at 1am on the last Sunday in March, March 29th. They will move their clocks back an hour at 1am on the last Sunday in October, October 25th.
July 25th will be on a Sunday the year 2017.
If the 25th of April is a Sunday, then Christmas Day in the same year is always a Saturday.
That is true only in regular years. When October 1st falls on a Sunday in the year before a leap year, in the leap year it falls on a Tuesday.
On Sunday the 25th of october at 02:00 gmt the clocks go back one hour to 01:00
It doesn't. The 25th of December 2016 is a Sunday. It was on a Friday in 2015 and as 2016 is a leap year, it skips an extra day and is on a Sunday in 2016, not Monday. It will be on a Monday in 2017.
October 20 was on a Sunday in the year 2013.
December 25th, this year it falls on a Sunday.
In a 28-year span from 1984 to 2011, October 24 fell on a Sunday in the following years: 1993 1999 2004 2010 For more such years, add 28 to these years.
From now until the end of the 21st century, the 25th of October will be on a Monday in 2021, 2027, 2032, 2038, 2049, 2055, 2060, 2066, 2077, 2083, 2088, 2094 and 2100.
Christmas Day is always on the 25th of December and can fall on any day of the week in a normal year or a leap year. So the answer to your question is that in a leap year Christmas Day can be on Sunday, Monday, Tuesday, Wednesday, Thursday, Friday or Saturday.