At least the Swiss version has no expiration date. That said, the government communicated that it's currently valid for 6 month after the second jab. This is

At least the Swiss version has no expiration date. That said, the government communicated that it's currently valid for 6 month after the second jab. This is because the length of effectiveness of the vaccination is not reliably known. I don't know how it works with certificates, which are issued based on a negative test.