What time is it? No one knows for sure. In a controversy reminiscent of the Year 2000 bug, experts can’t agree about whether to continue the long-standing practice of inserting occasional “leap seconds” into coordinated universal time, Nature reports today.

Since 1972, 32 leap seconds have been added to universal time to keep it in synch with the rotation of the Earth as it slows down, which is needed to keep telescopes functioning properly.

But continuing that practice could confuse sensitive aircraft navigation systems (GPS time can’t be adjusted), creating the possibility of accidents.

The International Telecommunication Union (ITU) will decide the issue. When? No one knows.