convert hours since date to datetime format in r

Question

I've downloaded some climate data from a website and am trying to analyse it in R.

The time format for the data is hours since 1800-01-01 00:00. For example:

ss <- seq(447042,455802, length.out = 1461)

which shows data at 6 hour intervals.

How can I convert this to a an actual time in R. This example should give data for 1851:

1851-01-01 00:00
1851-01-01 06:00

and so on...

How can this be done?

Any advice would be appreciated.

Answer 1

I think you have a typo as well as incorrect calculations. Let's assume you want time in the future of 1880 rather than the past. So it might be 1951 you wanted? Then to convert hours to seconds which are the basis for the POSIXt classed objects, just multiply by 3600 = 60*60:

> tail( as.POSIXct(ss*3600,origin='1880-01-01 00:00') )
[1] "1931-12-30 04:00:00 PST" "1931-12-30 10:00:00 PST" "1931-12-30 16:00:00 PST"
[4] "1931-12-30 22:00:00 PST" "1931-12-31 04:00:00 PST" "1931-12-31 10:00:00 PST"

As you can see it's nowhere the year 1951 either, but maybe you had two digits off and you wanted 1931? Conversions that span the range of years before the onset of daylight savings time and cross century boundaries where leap years and leap seconds were used may not "line up" with your expectations.