Need to fill date series (monthly) in a large document

I have a large number of data in an excel sheet and I want to put monthly date like 1 to 6 January 2017 and after that 6 to 6 February 2017 then 1 to 6 March 2017 etc. and it will be continue automatically till the end.
Example:
1 A 01-Jan-17
2 b 01-Jan-17
3 c 01-Jan-17
4 d 01-Jan-17
5 A 01-Jan-17
6 b 01-Jan-17
7 c 02-Jan-17
8 d 02-Jan-17
9 A 02-Jan-17
10 b 02-Jan-17
11 c 02-Jan-17
12 d 02-Jan-17
13 A 03-Jan-17
14 b 03-Jan-17
15 c 03-Jan-17
16 d 03-Jan-17
17 A 03-Jan-17
18 b 03-Jan-17
19 c 04-Jan-17
20 d 04-Jan-17
21 A 04-Jan-17
22 b 04-Jan-17
23 c 04-Jan-17
24 d 04-Jan-17