[R] Convert Long DOY time format to yyyymmdd hh format

[Ogbos Okike]

Dear Experts,
I have a data spanning 56 years from 1963 to 2018.
The datetime format is in DOY hour:
1963 335 0
1963 335 1
1963 335 2
1963 335 3
1963 335 4
1963 335 5
1963 335 6
1963 335 7
1963 335 8
1963 335 9
1996 202 20
1996 202 21
1996 202 22
1996 202 23
1996 203 0
1996 203 1
1996 203 2
1996 203 3
2018 365 20
2018 365 21
2018 365 22
2018 365 23
When I used:
as.Date(335,origin="1963-01-01"), for the first row, I got:
[1] "1963-12-02"
This is the format I want, though it is not yet complete. Time is missing.

Again, I can't be doing this one after the other. I guess you have a
better way of handling this. I have spent some time trying to get it
right but I am really stuck. I would be most glad if you could spare
your busy time to help me again.

Thank you very much for your usual kind assistance.

Best regards
Ogbos