/**
 * A Gmail date filter for a half-open range of UTC days.
 *
 * The bounds are epoch seconds rather than `YYYY/MM/DD` because Gmail reads a
 * written date as "midnight on that date in the PST timezone" and names
 * seconds as the way to mean any other zone, while a message lands in a day
 * directory by its UTC `internalDate`. The two disagree by the account's
 * offset, so a written date would leave the first hours of the requested day
 * outside the query and every message in them out of the listing. The lower
 * bound is a second early because the operator's inclusivity at the exact
 * second is not documented: an extra message from the day before is dropped by
 * the bucketing, a missing one is not recoverable.
 */
export declare function spanToGmailQuery(start: string, end: string): string;
/**
 * A Gmail date filter for one day directory, null when the name is not a
 * well-formed calendar date.
 *
 * The round-trip check is what refuses an impossible day: `Date.UTC` rolls
 * 2026-02-30 into March rather than failing, where python's `date()` raises.
 */
export declare function dateDirToGmailQuery(name: string): string | null;
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