The difference between the dates in years

[Steven Schveighoffer]

On Saturday, 10 February 2024 at 15:53:09 UTC, Alexander Zhirov 
wrote:
> Is it possible to calculate the difference between dates in 
> years using regular means? Something like that
>
>
> ```
> writeln(Date(1999, 3, 1).diffMonths(Date(1999, 1, 1)));
> ```
>
> At the same time, keep in mind that the month and day matter, 
> because the difference between the year, taking into account 
> the month that has not come, will be less.
>
> My abilities are not yet enough to figure it out more elegantly.

OK, so I thought this was already taking into account the day of 
the month.

This is what I came up with:

```d
int diffMonthNew(Date d1, Date d2)
{
     auto diff = d1.diffMonths(d2);
     if(diff > 0)
         return diff + (d1.day < d2.day ? -1 : 0);
     else if(diff < 0)
         return diff + (d1.day > d2.day ? 1 : 0);
     return 0;
}
```

Then if you want the years, it would be `diffMonthNew(d1, d2) / 
12`

-Steve