title: Update crontab (Whenever gem)
body: <p>By executing the whenever --update-crontab command, the following error returns:</p>
  
  <pre><code>/usr/lib/ruby/vendor_ruby/whenever/cron.rb:132:in `parse_as_string': Couldn't parse: 31557600 (ArgumentError)
      from /usr/lib/ruby/vendor_ruby/whenever/cron.rb:112:in `parse_time'
      from /usr/lib/ruby/vendor_ruby/whenever/cron.rb:50:in `time_in_cron_syntax'
      from /usr/lib/ruby/vendor_ruby/whenever/cron.rb:42:in `output'
      from /usr/lib/ruby/vendor_ruby/whenever/cron.rb:36:in `block (2 levels) in output'
      from /usr/lib/ruby/vendor_ruby/whenever/cron.rb:35:in `each'
      from /usr/lib/ruby/vendor_ruby/whenever/cron.rb:35:in `block in output'
      from /usr/lib/ruby/vendor_ruby/whenever/cron.rb:34:in `each'
      from /usr/lib/ruby/vendor_ruby/whenever/cron.rb:34:in `output'
      from /usr/lib/ruby/vendor_ruby/whenever/job_list.rb:151:in `block (2 levels) in cron_jobs'
      from /usr/lib/ruby/vendor_ruby/whenever/job_list.rb:147:in `each'
      from /usr/lib/ruby/vendor_ruby/whenever/job_list.rb:147:in `block in cron_jobs'
      from /usr/lib/ruby/vendor_ruby/whenever/job_list.rb:146:in `each'
      from /usr/lib/ruby/vendor_ruby/whenever/job_list.rb:146:in `cron_jobs'
      from /usr/lib/ruby/vendor_ruby/whenever/job_list.rb:65:in `generate_cron_output'
      from /usr/lib/ruby/vendor_ruby/whenever.rb:10:in `cron'
      from /usr/lib/ruby/vendor_ruby/whenever/command_line.rb:54:in `whenever_cron'
      from /usr/lib/ruby/vendor_ruby/whenever/command_line.rb:106:in `updated_crontab'
      from /usr/lib/ruby/vendor_ruby/whenever/command_line.rb:35:in `run'
      from /usr/lib/ruby/vendor_ruby/whenever/command_line.rb:6:in `execute'
      from /usr/bin/whenever:41:in `&lt;main&gt;'
  </code></pre>
  
  <p>My schedule.rb file:</p>
  
  <pre><code>every 1.year do
    rake "maintenances:renew"
  end
  </code></pre>
  
  <p>Any ideas?</p>