relative time

_src/_layouts/link.html

@@ -28,7 +28,7 @@ layout: base
             </p>
     		<p class="byline author vcard source-org"><span class="by">by</span> <a class="fn" rel="author" href="/about/">{{ page.author }}</a></p>
             
-    		<p class="time">{{ page.date | date_to_string }} <span class="modtime"></span></p>
+    		<p class="time">{{ page.date | timeago }} <span class="modtime"></span></p>
         </footer>
     </article>
 

_src/_layouts/photo.html

@@ -23,7 +23,7 @@ layout: base
                 {{ page.categories | category_links }}
             </p>
     		<p class="byline author vcard source-org"><span class="by">by</span> <a class="fn" rel="author" href="/about/">{{ page.author }}</a></p>
-    		<p class="time">{{ page.date | date_to_string }} <span class="modtime"></span></p>
+    		<p class="time">{{ page.date | timeago }} <span class="modtime"></span></p>
         </footer>
     
     </article>

_src/_layouts/post.html

@@ -23,9 +23,9 @@ layout: base
                 {{ page.categories | category_links }}
             </p>
     		<div class="time">
-    		    <p>{{ page.date | date_to_string }}</p>
+    		    <p>{{ page.date | timeago }}</p>
     		    {% if page.moddate %}
-    		    <p class="modtime">updated: {{ page.moddate | date_to_string }}</p>
+    		    <p class="modtime">updated: {{ page.moddate | timeago }}</p>
     		    {% endif %}
     		</div>
         </footer>

_src/_plugins/timeago.rb

@@ -0,0 +1,109 @@
+# 
+# jekyll-timeago
+#
+# https://github.com/markets/jekyll-timeago
+# 
+
+module Jekyll
+  module Timeago
+
+    DAYS_PER = {
+      :days => 1,
+      :weeks => 7,
+      :months => 31,
+      :years => 365,
+    }
+
+    # Max level of detail
+    # years > months > weeks > days
+    # 1 year and 7 months and 2 weeks and 6 days
+    MAX_DEPTH_LEVEL = 4
+
+    # Default level of detail
+    # 1 month and 5 days, 3 weeks and 2 days, 2 years and 6 months
+    DEFAULT_DEPTH_LEVEL = 2
+
+    def timeago(input, depth = DEFAULT_DEPTH_LEVEL)
+      unless depth_allowed?(depth)
+        raise "Invalid depth level: #{depth.inspect}"
+      end
+
+      unless input.is_a?(Date) || input.is_a?(Time)
+        raise "Invalid input type: #{input.inspect}"
+      end
+
+      days_passed = (Date.today - Date.parse(input.to_s)).to_i
+      time_ago_to_now(days_passed, depth)
+    end
+
+    private
+
+    # Days passed to time ago sentence
+    def time_ago_to_now(days_passed, depth)
+      return "today"     if days_passed == 0
+      return "yesterday" if days_passed == 1
+      return "tomorrow"  if days_passed == -1
+
+      future   = days_passed < 0
+      slots    = build_time_ago_slots(days_passed.abs, depth)
+      sentence = to_sentence(slots)
+
+      if future
+        "in #{sentence}"
+      else
+        "#{sentence} ago"
+      end
+    end
+
+    # Builds time ranges: ['1 month', '5 days']
+    # - days_passed: integer in absolute
+    # - depth: level of detail
+    # - current_slots: built time slots
+    def build_time_ago_slots(days_passed, depth, current_slots = [])
+      return current_slots if depth == 0 || days_passed == 0
+
+      time_range = days_to_time_range(days_passed)
+      days       = DAYS_PER[time_range]
+      num_elems  = days_passed / days
+      range_type = if num_elems == 1
+        time_range.to_s[0...-1] # singularize
+      else
+        time_range.to_s
+      end
+
+      current_slots << "#{num_elems} #{range_type}"
+      pending_days  = days_passed - (num_elems*days)
+      build_time_ago_slots(pending_days, depth - 1, current_slots)
+    end
+
+    # Number of days to minimum period time which can be grouped
+    def days_to_time_range(days_passed)
+      case days_passed.abs
+      when 0...7
+        :days
+      when 7...31
+        :weeks
+      when 31...365
+        :months
+      else
+        :years
+      end
+    end
+
+    # Validate if allowed level of detail
+    def depth_allowed?(depth)
+      (1..MAX_DEPTH_LEVEL).include?(depth)
+    end
+
+    # Array to sentence: ['1 month', '1 week', '5 days'] => "1 month, 1 week and 5 days"
+    def to_sentence(slots)
+      if slots.length == 1
+        slots[0]
+      else
+        "#{slots[0...-1].join(', ')} and #{slots[-1]}"
+      end
+    end
+  end
+end
+
+Liquid::Template.register_filter(Jekyll::Timeago)