Include UID in ticket.

web.py

@@ -119,23 +119,28 @@ def sell_page():
                            title='Sell', event=event, products=products)
 
 
-def print_orders(event, orders):
+def print_orders(transaction, cat, orders):
     printer.open()
 
     printer.set(align='CENTER')
     printer.image('static/img/macao-logo-printer.png', impl='bitImageColumn')
 
     printer.set(align='CENTER', text_type='B')
-    printer.text(event.name.upper())
+    printer.text(transaction.event.name.upper())
     printer.text("\n\n")
 
     for o in orders:
         printer.set(align='LEFT', width=2, height=2)
         printer.text("{} x {}".format(o.quantity, o.product.name.upper()))
         printer.text("\n")
-
     printer.text("\n")
 
+    printer.set(align='RIGHT')
+    printer.text("{} #{}-{}-{}"
+                 .format(datetime.strftime(transaction.created_at,
+                                           "%Y-%m-%d %H:%M"),
+                         transaction.event.uid, transaction.uid, cat))
+
     printer.cut()
     printer.close()
     sleep(0.7)
@@ -153,7 +158,7 @@ def print_transaction(transaction):
         categorized_orders[uid].append(o)
 
     for cat, orders in categorized_orders.items():
-        print_orders(transaction.event, orders)
+        print_orders(transaction, cat, orders)
 
 
 @app.route('/sell', methods=['POST'])