This paper considers what factors determine the migration of overseas students, when students cross borders for higher education. We utilise a gravity model for international student mobility and derive estimates for a sample of 18 countries of destination and 38 countries of origin over the period 2005–11. Our results confirm that geographical distance and the presence of a common language are powerful in explaining bilateral student flows. Our most interesting finding is that time zone differences have a statistically significant and economically large effect in determining international student flows.