Also, I think my programmer friends would say that to assume counting starts at 1 is to guarantee you've just introduced a bug. 🙂
When it comes to reckoning years, counting does start at 1. Otherwise, children would celebrate their first birthdays after two years of life (and their 0th after 1 year). As @khurtwilliams points out above, the Gregorian calendar doesn’t include a Year Zero, and it would be quite odd if it did. Programming languages typically start with 0 because the decimal system would have to treat “10” as a single digit but for most purposes most of us start counting at 1, not at 0. It doesn’t make a lot of practical difference if people choose to celebrate a new decade, century or millennium a year early but ideally they should know they’re doing so.