It was a trick question, the rotters. I would like to think they were secretly hoping you'd come up with the FM analogue of something like 'African or European?' so that they would be able to welcome you into the club but I think they just wanted to use it as a screen.
There is no such object in the DMR universe called a time dimension. That is, there is no distinct object type called a time dimension. You only have measure dimensions and regular dimensions.
You create the dimension which represents time as a regular dimension and add member sorting in addition to what appropriate data exists in your source database and what you have modeled in the dimension itself. You are basically pretending that the dimension is a Time Dimension and making use of member relative functions ( tail, last, first child etc.).
That's done with member sorting. With member sorting you can use functions which assume that members are relative to each other in a timey-whimy way, such as this order. The first child function would return January as the member in this case.
Year Month key Month
2016 201601 January
2016 201602 February
2016 201603 March
Without member sorting rules, members are generated in the order that their keys appear in the database. If the records are not in the exact order that you want to use them as members, let's say as in the table below, the members would be generated in that order. With member sorting you can impose sorting rules (including stuff like handling for fiscal weeks (for example was January 1 and 2 part of the last fiscal week of 2015, their own miniweek of 2016, or was December 27 to 31 part of the first fiscal week of 2016 (or even another FY which is not very closely following the calendar year).
Year Month key Month
2016 201602 February
2016 201601 January
2016 201603 March