Narrative:

Landed at an intermediate stop approximately [20 minutes after tower opened] without contacting tower for landing clearance using position reports on the CTAF. I had a current airport facility directory that indicated the tower was in operation from XA00Z-XQ00Z. After landing; the tower controller informed me I had landed without a clearance. I informed him that the directory indicated tower was not operational until XA00Z. Controller insisted I must have an outdated AFD. After departing the airport after approximately 15 minutes in route back to destination airport the controller contacted me on tower frequency and informed me that the double cross symbol after the zulu times requires that a pilot subtract one hour from the times noted for states that observe daylight savings time. I looked in the AFD legend and did not find reference to these double cross symbols. The controller referenced section 6 of the directory legend descriptions where I eventually found reference to these symbols. There was no other traffic at the time and no conflict with any other aircraft to my knowledge. [I was] very disappointed to find that zulu times require conversions for daylight savings. I was under the impression that pilots used zulu times to avoid the confusion of time conversions and time zones. I have quizzed 10 instructors since my incident this morning and not one was familiar with the symbol for daylight savings time conversion and no one was able to find reference to it in the AFD legend.

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Original NASA ASRS Text

Title: A C182 pilot landed without clearance because he erroneously determined the Tower was not yet open when he converted Zulu to local time without accounting for daylight savings time shift.

Narrative: Landed at an intermediate stop approximately [20 minutes after Tower opened] without contacting Tower for landing clearance using position reports on the CTAF. I had a current airport facility directory that indicated the Tower was in operation from XA00Z-XQ00Z. After landing; the Tower Controller informed me I had landed without a clearance. I informed him that the directory indicated Tower was not operational until XA00Z. Controller insisted I must have an outdated AFD. After departing the airport after approximately 15 minutes in route back to destination airport the Controller contacted me on Tower frequency and informed me that the double cross symbol after the Zulu times requires that a pilot subtract one hour from the times noted for states that observe daylight savings time. I looked in the AFD legend and did not find reference to these double cross symbols. The Controller referenced section 6 of the directory legend descriptions where I eventually found reference to these symbols. There was no other traffic at the time and no conflict with any other aircraft to my knowledge. [I was] very disappointed to find that Zulu times require conversions for daylight savings. I was under the impression that pilots used Zulu times to avoid the confusion of time conversions and time zones. I have quizzed 10 instructors since my incident this morning and not one was familiar with the symbol for daylight savings time conversion and no one was able to find reference to it in the AFD legend.

Data retrieved from NASA's ASRS site as of April 2012 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.