1061: EST
This is comic 1061. It was posted on May 28, 2012.
Image text: The month names are the same, except that the fourth month only has the name 'April' in even-numbered years, and is otherwise unnamed.
Ok, so I'm not sure I understand the significance of "no 1958" or April not being named on even numbered years (anyone know? help me in the comments...)
The one obvious reference is to Narnian time, which is a reference to the fictitious world of Narnia in CS Lewis's The Lion, The Witch and The Wardrobe. In Narnia, time passes much more quickly than in the real world. You could be in Narnia for several days and only a few minutes would have passed in the real world. I'm not sure how the EST is synched with Narian time, but I'd love to see it in action.