Changing Dates as per production shift timings in R

i want to change the date of the data entry based on timestamp. Basically, the company starts its operations at 7:00am in morning and works till 6:59am next day. this entire duration is counted as 1 day. So basically 19th Nov 2020 would mean starting 19-11-2020 07:00 to 20-11-2020 06:59

i have this dataset

structure(list(Timestamp = structure(c(1593714765.03054, 1593714824.99918, 
1593714884.96776, 1593714945.01468, 1593715005.01454, 1593715064.98314, 
1593715125.03002, 1593715185.18608, 1593715244.99822, 1593715304.96657
), class = c("POSIXct", "POSIXt"), tzone = "Asia/Kolkata"), Date = structure(c(18446, 
18446, 18446, 18446, 18446, 18446, 18446, 18446, 18446, 18446
), class = "Date"), Time = c("00:02", "00:03", "00:04", "00:05", 
"00:06", "00:07", "00:08", "00:09", "00:10", "00:11"), `HCM 18` = c(7, 
8, 7, 8, 7, 7, 8, 7, 8, 7), `HCM 19` = c(8, 8, 8, 8, 8, 7, 8, 
8, 8, 8), `HCM 20` = c(7, 7, 7, 7, 8, 7, 4, 8, 7, 7), `HCM 21` = c(8, 
7, 8, 8, 8, 7, 8, 8, 8, 8), `HCM 22` = c(8, 7, 8, 7, 7, 8, 7, 
8, 7, 7), `HCM 23` = c(8, 7, 8, 8, 8, 7, 8, 8, 8, 8), `HCM 24` = c(7, 
7, 7, 6, 7, 7, 7, 6, 4, 0), `HCM 25` = c(8, 8, 8, 7, 8, 8, 8, 
7, 8, 8), `HCM 54` = c(7, 8, 8, 7, 6, 8, 7, 8, 8, 7), `HCM 55` = c(8, 
7, 8, 7, 8, 8, 7, 8, 8, 7), `HCM 56` = c(8, 8, 8, 7, 8, 8, 7, 
8, 8, 7), `HCM 57` = c(8, 8, 7, 8, 8, 7, 8, 8, 7, 8), `HCM 58` = c(8, 
8, 7, 8, 7, 8, 7, 8, 7, 8), `HCM 59` = c(8, 1, 6, 8, 8, 7, 8, 
8, 7, 8), `HCM 60` = c(8, 7, 8, 8, 7, 8, 8, 7, 8, 8)), row.names = c(NA, 
10L), class = "data.frame")

So now i need to change the date for time less than 7:00am to previous day.

i want to do this in R.