Specify plot xticks


I am fairly new to Matplotlib and appreciate your help with my question:

I am looking to generate a time series trend plots and include as my xtick labels a selective list of strings. For ex: Month/Year label for data corresponding to the 1st day of each month. I may be plotting 365 days of data but want to show only 12 xtick labels.

Would it be possible to specify grid lines for every 7 days of data for instance? This makes the grid line locations different from the xtick label locations.

I am sure there is support for such a feature in Matplotlib. I did look through the docs/forums but could not find much help.

Any suggestions will be much appreciated.