By default, the dates that appear in your PastBook have Month day, year format (e.g. February 21, 2015), when you use the PastBook website in the English language. For all the other languages, the European format DD/MM/YYYY (e.g. 21/2/2015) is set as default.
If you have created a Facebook or Instagram book, you can change the date according to your preferences. First, click the 
button in the upper, left-hand corner and you will find yourself on the editing page. Click the 
button and enable the “Show dates” option Then click “Show dates as” and choose the format that appeals to you most.