R: Splitting a Time Series into custom seasons

Question

I have a time Series DataFrame:

[https://www.dropbox.com/s/elaxfuvqyip1eq8/SampleDF.csv?dl=0][1]

My intention is to divide this DataFrame into different seasons according to:

1. winter: Dec Jan Feb
2. Pre-monsoon: Mar Apr May Jun15 (i.e. till 15th of June)
3. Monsoon: 15Jun Jul Aug Sep (i.e. from 15th of June)
4. Post-monsoon: Oct Nov.

I tried using openair package function

selectByDate()

But no luck yet. Being novice in R. Any help would be highly appreciated.

Thanks!