I was parsing an international date format, like this: 2011-08-04T11:23:21.345Z. After getting back December as the month for August, I was mildly perplexed. Here was the issue
From the Mozilla docs for parseInt: If the input string begins with "0", radix is eight (octal). This feature is non-standard, and some implementations deliberately do not support it (instead using the radix 10). For this reason always specify a radix when using parseInt.
Always specify a radix!!