Game days in San Andreas in not a terribly accurate measure. The value will increment when the clock rolls past 00:00 and when you save. So if you save a lot you'll have lots of days in your stats. You can't really tease out the days from the saves because the clock doesn't roll over if you save within 6 hours of midnight. I'm not sure how days are handled for getting busted or wasted before midnight.
There's also a hidden in-game calendar that can only be viewed with save editors. It doesn't come into play much outside of the gym equipment and the gym glitch. It's always leap year in San Andreas. btw. There is little association between the calendar progression and game days. A random selection of saves suggested that it takes about 200+ game days to progress one calendar year, at which point the gym glitch might start to appear.