An error occurred while using the utcal.nc function to converte the time amounts to UTC date.

[PanfengZhang]

An error occurred while using the utcal.nc function to converte the time amounts to UTC date.

The example of .nc data is from NCEP (https://psl.noaa.gov/thredds/fileServer/Datasets/ncep.reanalysis/Monthlies/surface/slp.mon.ltm.1991-2020.nc)

library(RNetCDF)

diri = "C:/Rmet/data/slp.mon.ltm.1991-2020.nc"
fin <- open.nc(diri)
time <- var.get.nc(fin, variable = "time")
time_units <- att.get.nc(fin, variable = "time", attribute = "units")

utcal.nc(time_units, time, type = "c")
##  [1] "0000-12-30 UTC" "0001-01-30 UTC" "0001-02-27 UTC" "0001-03-30 UTC"
##  [5] "0001-04-29 UTC" "0001-05-30 UTC" "0001-06-29 UTC" "0001-07-30 UTC"
##  [9] "0001-08-30 UTC" "0001-09-29 UTC" "0001-10-30 UTC" "0001-11-29 UTC"

utcal.nc(time_units, time, type = "s")
##  [1] "01-01-01 00:00:00" "01-02-01 00:00:00" "01-03-01 00:00:00"
##  [4] "01-04-01 00:00:00" "01-05-01 00:00:00" "01-06-01 00:00:00"
##  [7] "01-07-01 00:00:00" "01-08-01 00:00:00" "01-09-01 00:00:00"
## [10] "01-10-01 00:00:00" "01-11-01 00:00:00" "01-12-01 00:00:00"

When the type parameter is set to n or s, the returned dates are inconsistent. According to the metadata information of the data, it is known that it is correct when setting s.