I’m afraid that your ZULU to EST conversion was incorrect, as 0800Z is 3am EST (1pm EST is 1800Z). If it’s at 0800Z, great, but if it is at 1800Z, unfortunately it falls against the rules of the category that group flights posted in #live:groupflights must be within three hours of posting.
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Additionally, you are not allowed to include gates in any #live:groupflights flight. Refer to the “About the GroupFlights Category” topic @Thunderbolt linked.