05 - counting the days since an arbitrary date.rb

O Reilly Ruby Cookbook source code

def last_modified(file)
  t1 = File.stat(file).ctime
  t2 = Time.now
  elapsed = (t2-t1)/(60*60*24)
  puts "#{file} was last modified #{elapsed} days ago."
end

last_modified("/etc/passwd")
# /etc/passwd was last modified 125.873605469919 days ago.
last_modified("/home/leonardr/")
# /home/leonardr/ was last modified 0.113293513796296 days ago.
#---
require 'date'
def advent_calendar(date=DateTime.now)
  christmas = DateTime.new(date.year, 12, 25)
  christmas = DateTime.new(date.year+1, 12, 25) if date > christmas
  difference = (christmas-date).to_i
  if difference == 0
    puts "Today is Christmas."
  else
    puts "Only #{difference} day#{"s" unless difference==1} until Christmas."
  end
end

advent_calendar(DateTime.new(2006, 12, 24))
# Only 1 day until Christmas.
advent_calendar(DateTime.new(2006, 12, 25))
# Today is Christmas.
advent_calendar(DateTime.new(2006, 12, 26))
# Only 364 days until Christmas.
#---
sent = DateTime.new(2006, 10, 4, 3, 15)
received = DateTime.new(2006, 10, 5, 16, 33)
elapsed = (received-sent) * 24
puts "You responded to my email #{elapsed.to_f} hours after I sent it."
# You responded to my email 37.3 hours after I sent it.
#---
require 'date'
def remaining(date, event)
  intervals = [["day", 1], ["hour", 24], ["minute", 60], ["second", 60]]
  elapsed = DateTime.now - date
  tense = elapsed > 0 ? "since" : "until"
  interval = 1.0
  parts = intervals.collect do |name, new_interval|
    interval /= new_interval
    number, elapsed = elapsed.abs.divmod(interval)
  "#{number.to_i} #{name}#{"s" unless number == 1}"
  end
  puts "#{parts.join(", ")} #{tense} #{event}."
end

remaining(DateTime.new(2006, 4, 15, 0, 0, 0, DateTime.now.offset),
          "the book deadline")
# 27 days, 4 hours, 16 minutes, 9 seconds until the book deadline.
remaining(DateTime.new(1999, 4, 23, 8, 0, 0, DateTime.now.offset),
          "the Math 114A final")
# 2521 days, 11 hours, 43 minutes, 50 seconds since the Math 114A final.
#---