Convert a cell into datetime

 By using 'unstack' command I get two tables (Below is 1 and other one is of similar format to this one)

Now my datetime has converted into 'var'. Actually I want to get the common dates with associated PM value of these two tables based on the row. For example: for station '120010023' (Row1) of this table) with the another table. That's why I transpose the tables and also insert the date 'var' into a column (below).

 But I am not getting any way to convert this 'x01_jan_2013' into datetime. I thought I will convert the first column of two tables into datetime and run the innnerjoin command. 
Could anyone help me please. Or, there is any easier way to find out the common dates and associated values for a specific station between two tables.Thanks in advance.

[Peter Perkins]

Sadia, I think you're going to need to present a short clear example of what you are starting with and what you want to end up with. Things like 'x01_jan_2013' are an artifact of unstacking using a datetime variable. I think you want to avoid that, but without more information, it's hard to know how.