After how many days after unprotected sex is chlyamydia urine test accurate?

Fairly soon: The test you're referring to is the Nucleic Acid Amplification Test or NAAT. It's very good at detecting the DNA of chlamydia in the urine even at low concentrations. The test will be positive within a few days of infection and is very accurate in identifying the infection specifically as chlamydia. It may actually be a better test than the traditional cervical swab.

Soon after: Within a week is provides reasonable sensitivity for Chlamydia, but your provider may encourage you to come back even if the testing is negative particularly in the first couple days of exposure for a repeat test within 2 weeks to ensure that better specificity.