Convert AWS maintenance window between timezones.

aws_maintenance_window.rb

#!/usr/bin/env ruby

def offset_maintenance_window(w, offset=-7)
  days = %w[mon tue wed thu fri sat sun]
  if /(?<day_start>[a-z]{3}):(?<hour_start>\d\d):(?<minute_start>\d\d)-(?<day_end>[a-z]{3}):(?<hour_end>\d\d):(?<minute_end>\d\d)/ =~ w
    day_start = days.find_index(day_start)
    day_end = days.find_index(day_end)
    hour_start = hour_start.to_i + offset
    minute_start = minute_start.to_i
    hour_end = hour_end.to_i + offset
    minute_end = minute_end.to_i
    if hour_start < 0
      hour_start += 24
      day_start -= 1
      day_start = days.length-1 if day_start < 0
    elsif hour_start > 23
      hour_start -= 24
      day_start += 1
      day_start = 0 if day_start >= days.length
    end
    if hour_end < 0
      hour_end += 24
      day_end -= 1
      day_end = days.length-1 if day_end < 0
    elsif hour_end > 23
      hour_end -= 24
      day_end += 1
      day_end = 0 if day_end >= days.length
    end
    "%s:%02d:%02d-%s:%02d:%02d" % [days[day_start], hour_start, minute_start, days[day_end], hour_end, minute_end]
  else
    "could not parse maintenance window"
  end
end

w = "wed:03:08-wed:03:38"
puts "#{w} => #{offset_maintenance_window(w, -7)}"

# wed:03:08-wed:03:38 => tue:20:08-tue:20:38