Rough estimate using 30 days as average month would be ~35 months (1050 = 35×30). The average month is a tad longer than 30 days, but I don’t know exactly how much. Without a calculator, I’d guess the total result is closer to 34.5. Just using my own brain, this is as far as I get.

Now, adding a calculator to my toolset, the average month is 365.2425 d / 12 m = 30.4377 d/m. The total result comes out to about 34.2, so I overestimated a little.

Also, the total time is 1041.66… which would be more correctly rounded to 1042, but has negligible impact on the redult.