Incompatible methods ("Ops.data.frame", "-.POSIXt") for "-"

This error message is indicating that you are trying to perform subtraction (-) between two objects of different classes, specifically between a data frame and a POSIXt object.

To fix this error, you should check the objects you are trying to subtract and make sure they are both of the same class. If they are not, you may need to convert them to the same class before performing the subtraction.

For example, if you want to subtract a column of dates (stored as POSIXt objects) from a data frame, you could extract the column of dates and convert it to a data frame before performing the subtraction:

# example data frame with a column of dates
df <- data.frame(x = 1:5, date = Sys.time() + 1:5)

# extract the column of dates and convert to data frame
date_df <- data.frame(date = df$date)

# perform subtraction between the two data frames
result <- df - date_df

Alternatively, if you only need to subtract a specific date or time from a POSIXt object, you can use the `as.numeric` function to convert the POSIXt object to a numeric representation of seconds since the epoch, subtract your desired value in seconds, and then convert back to a POSIXt object:

# example POSIXt object
my_time <- as.POSIXct("2022-01-01 12:00:00")

# subtract 1 hour from my_time
new_time <- as.POSIXct(as.numeric(my_time) - 3600, origin = "1970-01-01")