Do these numbers correspond to sequential months? If so you can create a mapping using a dictionary.
Here I am using datetime(year, month, day).strftime(format)
to get "Jan, 1970" type strings.
>>> from datetime import datetime
>>> l = [710040, 710784, 711456, 712200, 712920, 713664,
... 714384, 715128, 715872, 716592, 717336, 718056,
... 718800, 719544, 720216, 720960, 721680, 722424]
>>> mapping = {
... num : datetime(1970 + i // 12, i%12 + 1, 1).strftime('%b, %Y')
... for i, num in enumerate(l)
... }
which gives
>>> mapping
{710040: 'Jan, 1970', 710784: 'Feb, 1970', 711456: 'Mar, 1970', 712200: 'Apr, 1970', 712920: 'May, 1970', 713664: 'Jun, 1970', 714384: 'Jul, 1970', 715128: 'Aug, 1970', 715872: 'Sep, 1970', 716592: 'Oct, 1970', 717336: 'Nov, 1970', 718056: 'Dec, 1970', 718800: 'Jan, 1971', 719544: 'Feb, 1971', 720216: 'Mar, 1971', 720960: 'Apr, 1971', 721680: 'May, 1971', 722424: 'Jun, 1971'}