I don't have a wide spread of weight but I was 125 in January of 2015, was 138 in December, then I got back down to 127 by March. I gained again in the summer, hitting 140lbs in September of 2016. Taking into acount the months I was actually gaining, I wanna say it took a grand total of 15-16 months. Both times I actively gained, I effectively gained the same amount of weight. The second time happened in about three months. Currently at 131lbs.
I was 183-185 when I got married in 1983. I joined the military reserves and spent twenty five years serving, but my weight gradually went up, despite running every day etc. In 2013 I retired from the reserves I was at 207 lbs. Now I at 225 lbs. gradually gaining, just enjoying eating what I want and how much. I not sure how much weight I'm going to gain, just enjoying the ride.
It took me me six months and nine days to go from 187-234.
I plan on surpassing that measly little 234 soon though. The habits I built in that half year have been established and there is no way out, except by an incredible amount of will. And why stop when gaining is so much fun?
I did most of my gaining as a teen, so my adult gain is really modest. I was 245 by the time I was 16, and I didn't gain past that until I was 22 or 23. From there, it took me two years (off and on) to get to my peak of 285.