excel_numeric_to_date {janitor}

Convert dates encoded as serial numbers to Date class.

Description

Converts numbers like 42370 into date values like 2016-01-01.

Defaults to the modern Excel date encoding system. However, Excel for Mac 2008 and earlier Mac versions of Excel used a different date system. To determine what platform to specify: if the date 2016-01-01 is represented by the number 42370 in your spreadsheet, it's the modern system. If it's 40908, it's the old Mac system. More on date encoding systems at http://support.office.com/en-us/article/Date-calculations-in-Excel-e7fe7167-48a9-4b96-bb53-5612a800b487.

A list of all timezones is available from base::OlsonNames(), and the current timezone is available from base::Sys.timezone().

If your input data has a mix of Excel numeric dates and actual dates, see the more powerful functions convert_to_date() and convert_to_datetime().

Usage

excel_numeric_to_date(
  date_num,
  date_system = "modern",
  include_time = FALSE,
  round_seconds = TRUE,
  tz = Sys.timezone()
)

Arguments

date_num

numeric vector of serial numbers to convert.

date_system

the date system, either "modern" or "mac pre-2011".

include_time

Include the time (hours, minutes, seconds) in the output? (See details)

round_seconds

Round the seconds to an integer (only has an effect when include_time is TRUE)?

tz

Time zone, used when include_time = TRUE (see details for more information on timezones).

Details

When using include_time=TRUE, days with leap seconds will not be accurately handled as they do not appear to be accurately handled by Windows (as described in https://support.microsoft.com/en-us/help/2722715/support-for-the-leap-second).

Value

Returns a vector of class Date if include_time is FALSE. Returns a vector of class POSIXlt if include_time is TRUE.

See Also

Other Date-time cleaning: convert_to_date(), sas_numeric_to_date()

Examples

excel_numeric_to_date(40000)
excel_numeric_to_date(40000.5) # No time is included
excel_numeric_to_date(40000.5, include_time = TRUE) # Time is included
excel_numeric_to_date(40000.521, include_time = TRUE) # Time is included
excel_numeric_to_date(40000.521, include_time = TRUE,
  round_seconds = FALSE) # Time with fractional seconds is included