如何为月份名称分配一个数字 - 机器人框架

I am getting a time stamp by reading a field in my page which has the month name in it like "Feb 28, 2015 12:59". I want to verify which month name it is and assign it the month number. I want to get the date such as "5 28, 2015 12:59". I have divided the time stamp and I am trying to convert the month name to number as below:I am getting a time stamp by reading a field in