General aviation pilot reported a discrepancy at GOV airport between the ATIS and published frequencies and stated the NOTAM has expired and is unclear as to what the correct Tower/CTAF frequency is. The reporter noted this could lead to pilots communicating on different frequencies; potentially causing traffic conflicts.

Narrative

I departed GOV yesterday; Day 0; and arrived GOV today; Day 1. On both occasions; I listened to the ATIS broadcast. There was a recorded message included with the ATIS that the CTAF and Tower frequency is 124.65. This disagreed with published frequencies; and there was no current NOTAM.The published frequency for GOV Tower / CTAF is 126.2. There is an expired NOTAM (which expired a few days prior); which temporarily changed the published frequency 126.2 to 124.65. It appears to me the field operators failed to notice or change the recorded message included with the ATIS; even though the NOTAM about changed frequencies is now expired. Or; they failed to extend the NOTAM. It's unclear which.The Tower was closed during the times of my flights; so I was unable to ask a Local Controller about which frequency to use. Since I was concerned that other pilots might not all be on the same frequency; I ended up tuning one radio to 124.65 and the other to the published frequency 126.2; and monitoring both frequencies. As another human factor; there is often not a lot of traffic at GOV; which can also lead to complacency if a pilot doesn't hear anybody on the radio when the Tower is closed. A pilot might not question why they weren't hearing anybody else. At the very least; this added unnecessary workload and distraction at a critical phase of flight. At worst; this could have caused an unexpected traffic conflict resulting in collision if one pilot was self-announcing on the frequency advertised on the ATIS (124.65); while another pilot was self-announcing on the frequency listed in the A/FD and on IAPs (126.2). Once airborne on departure on Day 0; I did contact Minneapolis Center (on 132.9) to ask if they had any late-published NOTAMs that were not included in my preflight briefing. They did not. I asked them to pass a message to GOV Tower / Operations regarding the issue; which they said they would; but advised that nobody would see for several days while the Tower was closed.