Time here is something heavy that people carry and cannot escape. The speaker imagines the earth as a clock, but not a friendly one: it belongs to "them," a group the speaker watches from the outside. Their eyes and shoulders droop, and frost seems to settle on their faces, as if the years are slowly wearing them down. The clock "dictates beginnings and endings," and the people want only one thing from it, more time. It refuses. It "just presses on."
The speaker sounds like a quiet, slightly sad observer, someone who sees the exhaustion without being able to help. The short, blunt lines near the end ("Cold. Heavy.") make time feel relentless and unfeeling. The final lines add a sense of unease, because nobody knows where the clock began or where it will stop. The mood is wintry and resigned, with a small note of awe at how large and mysterious time really is.