Class: DateTime

Inherits:
Object
  • Object
show all
Defined in:
lib/boris/core_ext/datetime.rb

Class Method Summary collapse

Class Method Details

.parse_start_date(base_time, time_elapsed) ⇒ DateTime

Returns a new DateTime object showing the exact date and time that something occurred by using the difference in time between a date and the time that has elapsed. This is used to calculate the exact date and time that something occurred when we only know the current time and the time that elapsed since that event occurred.

For example, in UNIX, we can’t easily determine when a process was kicked off (by using data from the ‘ps’ command). But the ‘ps’ command will show us the time elapsed, so coupling that data with the current time, we can figure out when that process was started.

now = DateTime.parse('2013-04-12T12:00:00-04:00')
process_run_time = '1-05:59:59'
DateTime.parse_start_date(now, process_run_time) #=> #<DateTime: 2013-04-11T10:00:01-04:00>

Parameters:

  • base_time —

    the base DateTime to calculate from (typically the current time)

  • time_elapsed —

    String showing the time elapsed (format: %d-%H:%M:%S)

Returns:

  • (DateTime) —

    a new DateTime object showing the start date/time



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# File 'lib/boris/core_ext/datetime.rb', line 21

def self.parse_start_date(base_time, time_elapsed)
  time_elapsed = "0-#{time_elapsed}" unless time_elapsed =~ /-/

  time_elapsed = time_elapsed.split('-')
  days_back = time_elapsed[0].to_i
  time_elapsed = time_elapsed[1].split(':')
      
  hours_since = time_elapsed[0].to_i
  minutes_since = time_elapsed[1].to_i
  seconds_since = time_elapsed[2].to_i

  seconds_since += minutes_since * 60
  seconds_since += hours_since * 60 * 60
  seconds_since += days_back * 60 * 60 * 24
  
  started_on = (base_time.to_time - seconds_since).to_datetime
end