x <- as.POSIXct("2012-03-26 23:12:13", tz = "Etc/GMT+8")
date(x)
as.Date(x) # by default as.Date assumes you want to know the date in UTC
as.Date(x, tz = "Etc/GMT+8")
date(x) <- as.Date("2000-01-02")
x
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