Every 28 years
24 years
It is the way calendars work. Friday is 5 days after Sunday, but there will be at least one leap year in that period, which means one day will be skipped, so it only takes 4 years to reach Friday. That same pattern continues, in that although Wednesday is 5 days later, it will come round in 4 years due to a leap year. Yet again, Monday is 5 years after Wednesday, but the leap year will make it only take 4 years to come round. There are many patterns like that in calendar dates.
Just twice, in 1995 and 2006. It may seem very few, but this is due to leap year causing a Wednesday to be skipped.
Non-leap years that start on a Sunday and all years that start on a Saturday, which is 24.75% of all years, have 260 weekdays. Non-leap years that start on a weekday and leap years that start on a Sunday or a Friday, which is 61.75% of all years, have 261 weekdays. Leap years that start on Monday, Tuesday, Wednesday or Thursday, which is 13.5% of all years, have 262 weekdays.
As of 2011, the leap years since 1974 have fallen in the following years: 1976 1980 1984 1988 1992 1996 2000 2004 2008 The next leap year will fall in 2012.
80 years = 2,524,651,960 secondsUsing: 1 year = 365.25636 days
Approximately 133682 days. The exact number will depend on the number of leap years that fall in that range.
262 in leap years that begin on Monday, Tuesday, Wednesday or Thursday 261 in leap years that begin on Sunday or Friday and regular years that begin on any weekday 260 in any year that begins on a Saturday and regular years that begin on Sunday
16 leap years
It will be 11 years from 2014. 2025 will be the next year that will have the same combination of days and dates as 2014 does. 2020 will also start on a Wednesday, but as it is a leap year, and 2014 isn't, it will have a different combination for most of the year. So the next non-leap year that starts on a Wednesday is 2025.
24 leap years
Leap years occur every 4 years.