What does the "0"mean in "d0my"

General
1 
parse_date_time("string", orders = "d0mY", "0mY", "Y")
2

Are you sure you didn't mean to write:

parse_date_time("string", orders = c("d0mY", "0mY", "Y"))

Stephen

3

From the documentation for lubridate::parse_date_time:

Om
Matches numeric month and English alphabetic months (Both, long and abbreviated forms).

Note that it is an uppercase O, not a 0 (zero).

Disclaimer: I am not a frequent user of {lubridate}, so there may be both 0m and Om.