{"slug":"why-spreads-widen-at-the-open","qid":"window_guard","label":"Window guard: the UTC session filter maps to a 9:30 a.m. ET start on both ends of the rolling window","post_title":"Why Are Spreads Wider at the Open? Real Data","post_url":"/blog/why-spreads-widen-at-the-open#q-window_guard","columns":["win_start_et_min","win_end_et_min"],"rows":[{"win_start_et_min":570,"win_end_et_min":570}],"shape":"scalar","sql":"SELECT toHour(toTimeZone(toDateTime(today() - 14) + toIntervalMinute(810), 'America/New_York')) * 60\n         + toMinute(toTimeZone(toDateTime(today() - 14) + toIntervalMinute(810), 'America/New_York')) AS win_start_et_min,\n       toHour(toTimeZone(toDateTime(today() - 4) + toIntervalMinute(810), 'America/New_York')) * 60\n         + toMinute(toTimeZone(toDateTime(today() - 4) + toIntervalMinute(810), 'America/New_York')) AS win_end_et_min","computed_at":"2026-08-08T04:51:07.468265+00:00","elapsed":0.00561301}