UK university students believe the EU referendum is key to their future, but almost two-thirds do not know when it is, suggests research.
And a third of more than 2,000 students questioned feared being unable to get to their polling station on the day.
The referendum, on 23 June, is outside term time, so many students will need to re-register at their home address, says the National Union of Students.
NUS vice-president Richard Brooks urged students "to think ahead".
"The EU referendum is a once-in-a-generation vote," said Mr Brooks.
"The decision made on the 23 June will impact young people and students the most, as they are the ones that will live with the consequences for the longest.
"If students don't want their future decided for them, it is essential that as many as possible get out and vote."
Mr Brooks urged students to think about where they would be on referendum day and to make sure they register or re-register at the right address.
"If they are unsure about where they will be, students can register at both their term-time and home address, providing they only vote once," he said.
"If they are going to be on holiday or are heading to Glastonbury, they should apply for a postal vote."
People had until 17:00 on 7 June to register if they wanted to vote in the referendum, he added.
It is also possible to apply for a postal or proxy vote by 17:00 on 8 June.
The interviews, carried out this month on a representative sample of students from across the UK by YouthSight for Universities UK, found:
- 63% were unable to name the date of the referendum
- 54% were unable to name the month
- 72% said the outcome would have a significant impact on their future
- 32% feared being unable to vote as they would be on holiday or no longer living at the term-time address where they are registered
Universities UK and the Association of Colleges are holding voter registration drives at institutions across the UK.
Students will be advised to register, re-register or apply for proxy or postal votes, according to their circumstances.
UUK chief executive Nicola Dandridge said it was of "real concern" that so many students were unaware of the referendum date and that they might have to re-register to vote at another address.
"From this week, universities will be scaling up their efforts to encourage students to register to vote, and to make sure they do so in the right location," she said.
"With nearly two million UK students eligible to vote in the referendum, it is vital that they have all the necessary information to make sure they can take part in this hugely important decision."