Medela is introducing a Breastmilk Labeling system in January. These new lids will allow you to twist to the day of the week the milk was pumped and also to am/pm.
They are being sold as a pack or as part of a storage system tub for the fridge or freezer. The tub allows you to organize the bottles in a row by date. Also look for a new phone app, an updated Pump In Style Advanced and an updated breastmilk bag.