According to Scottforbes.net, on average it happens once every seven years, but the pattern is complicated by the subtleties of the Gregorian calendar.
Thanksgiving is always on the fourth Thursday in November, which means the holiday always falls between November 22nd and 28th. The simple formula for calculating the date of Thanksgiving is to take last year’s date and subtract a day, and then add seven days if you’ve ended up on the 21st… so if Thanksgiving 2009 was on the 26th (which it was), then Thanksgiving 2010 is on the 25th, and in 2011 it’ll be on the 24th.
But then things start getting complicated, because 2012 is a leap year. Thanksgiving 2012 is on the 22nd, not the 23rd – that extra day in February pushes us back two days instead of just one. And then, in 2013, we wrap around: One day earlier than the 22nd would be the 21st, but now we’re looking at the third Thursday of the month, so we add seven days to get Thanksgiving on the 28th.
All this adds up to a pattern that takes 2800 years to go through a full cycle. Therefore, in the short term (that is, from 1901 to 2100) there’s a leap year every four years, and November 26 will be on Thanksgiving four times out of every 28: If November 26 falls on Thanksgiving in a given year, then it falls on Thanksgiving again exactly 28 years later, and three other times in between at intervals of six years, five years, six years, and then eleven years.
Here’s a list of the years between now and 2100 when Thanksgiving falls on November 26:
2015
2020
2026
2037
2043
2048
2054
2065
2071
2076
2082
2093
2099
Tip! View a list of Thanksgiving Day dates in the following years at Timeanddate.com.