# From Date
as_iso_year_week_day(as.Date("2019-01-01"))
# From POSIXct, which assumes that the naive time is what should be converted
as_iso_year_week_day(as.POSIXct("2019-01-01 02:30:30", "America/New_York"))
# From other calendars
as_iso_year_week_day(year_quarter_day(2019, quarter = 2, day = 50))
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