Normalizes Date, POSIXct, or ISO 8601 strings into canonical UTC strings
with trailing Z. Supported inputs are:
Date(interpreted as midnight UTC)POSIXct/POSIXt"YYYY-MM-DD""YYYY-MM-DDTHH:MM:SS""YYYY-MM-DDTHH:MM:SSZ"
Examples
iso_utc("2020-01-01")
#> [1] "2020-01-01T00:00:00Z"
iso_utc(as.POSIXct("2020-01-01 09:30:00", tz = "UTC"))
#> [1] "2020-01-01T09:30:00Z"