My dataframe have one column date which has the following data:
0         2019/5/20 22:49:29
1         2019/5/20 23:18:23
2           2019/3/8 9:11:35
3           2019/3/8 9:19:58
4         2019/5/20 22:57:12
5           2019/3/8 9:06:41
How can I convert it to format year-month:
0         2019-05
1         2019-05
2         2019-03
3         2019-03
4         2019-05
5         2019-03
Thank you.
