# build a data.table
require(data.table)
data_set <- data.table( column1 = as.Date("2016-01-01"), column2 = as.POSIXct("2017-01-01") )
# Use the function
data_set = date_format_unifier(data_set, format = "Date")
# Control result
sapply(data_set, class)
# return Date for both columns
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