UTC-seconds of a known session open. Buckets align to it so e.g. 5-minute bars start at 09:15, not at an arbitrary epoch floor. Defaults to 0 (epoch).
'ltq-sum' accumulates last-traded-qty; 'day-delta' diffs cumulative day volume.
UTC-seconds of a known session open. Buckets align to it so e.g. 5-minute bars start at 09:15, not at an arbitrary epoch floor. Defaults to 0 (epoch).