Narrative:

Aircraft X came onto my frequency; enroute to ZZZ. I gave him an initial descent and reviewed the notams for ZZZ (where he was landing). I observed a number of new notams that I had not seen before. Among the notams was this one:'ZZZ 07/025 ZZZ runway 1/19 ..clsd.. 1507[day]XD22-1508[day]XD20EST'i asked the pilot if he had the current weather and notams and for his approach request. He replied that he had weather and notams and was planning a visual approach. Since the pilot said he had the notams; I confirmed with him that he was aware of the NOTAM for the runway closure. He replied that he was not familiar with it. I decided to read him that NOTAM and the other notams since there was a disconnect.the way the NOTAM is written is ambiguous. The 'EST' at the end of the termination time caused me to think 'eastern standard time.' I questioned the time of the time of the NOTAM since there was no 'Z' or 'EST' next to it. I told the pilot we would look into the situation and let him know.I asked the controller in charge to investigate the NOTAM. He called the airport manager who confirmed that the time was local time (xd:20). Since it was approximately xa:30; we understood this to mean that the runway was still open and would be open for approximately 3 more hours. I passed this information on to the pilot who intended to land on that runway. The pilot cancelled IFR a number of miles away from the airport and I terminated radar services and issued a frequency change.another aircraft; aircraft Y; on the ground at ZZZ called for his clearance and told me he was planning to depart runway 28 since the primary runway was closed. I passed on the information we received from the airport manager to aircraft Y about the runway being open for a few more hours. Prior to obtaining his release; aircraft Y called on the frequency again to report that he witnessed aircraft X change runway at the last minute because runway 1/19 was indeed closed. Aircraft Y told me that the aircraft X was on approximately a 2 mile final and had to abandon his approach to landing and circle to the other runway to avoid hitting personnel and equipment on the runway.another aircraft; a VFR cessna; who was flying over ZZZ reported that he observed 'a dozen vehicles at the approach end of runway 19'. Change the format for notams to remove any reference to 'EST' as this can easily be confused with 'eastern standard time'. In this case; the issuer meant for 'EST' to mean estimated. This ambiguity caused a lot of confusion. Apparently even the airport manager was confused about the start time of the NOTAM since he told the controller in charge the runway was open until XD20 local time.better communication needs to be put in place when runways are closed. There should be no doubt or confusion about the status of a runway. The airport manager should have known the runway was closed at that time and should have been very specific in stating that the runway was currently closed.

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Original NASA ASRS Text

Title: Controllers report of the letters 'EST' in the end of a NOTAM and the confusion it cost. The Controller thought EST meant Eastern Standard Time; but actually meant estimated. The Controller had aircraft going into the airport to a closed runway thinking it was open. The Controller checked with the Airport Manager who said it was open. An aircraft had to make a missed approach due to men and equipment on the runway.

Narrative: Aircraft X came onto my frequency; enroute to ZZZ. I gave him an initial descent and reviewed the NOTAMs for ZZZ (where he was landing). I observed a number of new NOTAMs that I had not seen before. Among the NOTAMs was this one:'ZZZ 07/025 ZZZ RWY 1/19 ..CLSD.. 1507[day]XD22-1508[day]XD20EST'I asked the pilot if he had the current weather and NOTAMs and for his approach request. He replied that he had weather and NOTAMs and was planning a visual approach. Since the pilot said he had the NOTAMs; I confirmed with him that he was aware of the NOTAM for the runway closure. He replied that he was not familiar with it. I decided to read him that NOTAM and the other NOTAMs since there was a disconnect.The way the NOTAM is written is ambiguous. The 'EST' at the end of the termination time caused me to think 'Eastern Standard Time.' I questioned the time of the time of the NOTAM since there was no 'Z' or 'EST' next to it. I told the pilot we would look into the situation and let him know.I asked the CIC to investigate the NOTAM. He called the airport manager who confirmed that the time was LOCAL time (XD:20). Since it was approximately XA:30; we understood this to mean that the runway was still open and would be open for approximately 3 more hours. I passed this information on to the pilot who intended to land on that runway. The pilot cancelled IFR a number of miles away from the airport and I terminated radar services and issued a frequency change.Another aircraft; Aircraft Y; on the ground at ZZZ called for his clearance and told me he was planning to depart runway 28 since the primary runway was closed. I passed on the information we received from the airport manager to Aircraft Y about the runway being open for a few more hours. Prior to obtaining his release; Aircraft Y called on the frequency again to report that he witnessed Aircraft X change runway at the last minute because runway 1/19 was indeed closed. Aircraft Y told me that the Aircraft X was on approximately a 2 mile final and had to abandon his approach to landing and circle to the other runway to avoid hitting personnel and equipment on the runway.Another aircraft; a VFR Cessna; who was flying over ZZZ reported that he observed 'a dozen vehicles at the approach end of runway 19'. Change the format for NOTAMs to remove any reference to 'EST' as this can easily be confused with 'Eastern Standard Time'. In this case; the issuer meant for 'EST' to mean Estimated. This ambiguity caused a lot of confusion. Apparently even the airport manager was confused about the start time of the NOTAM since he told the CIC the runway was open until XD20 Local time.Better communication needs to be put in place when runways are closed. There should be no doubt or confusion about the status of a runway. The airport manager should have known the runway was closed at that time and should have been very specific in stating that the runway was currently closed.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.