I'm no expert on this and checked wikipedia about beacons, but found no info regarding default content(s) of a beacon. I find it curious that Dan's beacon had inside a timer, and a timer only- as if Dan and the people on the freighter were already aware of some temporal discrepancies regarding the island. I think Dan was surprised not necessarily about the time difference itself, but that there was something even more peculiar about it. Like some unexpected change in its tendency or something..

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"Bear...? Is that you?"-- Hurley S03E4