Bug: relative dates use elapsed time instead of calendar days

[zengen-dermot]

Bug

When displaying due dates with relative formatting, the tool calculates based on elapsed time rather than calendar day boundaries. This causes confusing output where a task due in 2 calendar days shows as "in 1 day".

Example

• Now: Thursday, January 8, 2026 at 9:00am
• Task due: Saturday, January 10, 2026 at 8:00am

Expected: "in 2 days" (Thursday → Friday → Saturday)
Actual: "in 1 day" (~47 hours elapsed ÷ 24 ≈ 1.9, displayed as 1)

Reproduction

# On Thursday morning:
reminders add To-Dos "Saturday morning meeting" --due-date "2026-01-10 08:00"
reminders show To-Dos
# Shows "in 1 day" instead of "in 2 days"

Location

Sources/RemindersLibrary/Reminders.swift, lines 7-11:

private let dateFormatter = RelativeDateTimeFormatter()
private func formattedDueDate(from reminder: EKReminder) -> String? {
    return reminder.dueDateComponents?.date.map {
        dateFormatter.localizedString(for: $0, relativeTo: Date())
    }
}

RelativeDateTimeFormatter.localizedString(for:relativeTo:) uses elapsed time rather than calendar day boundaries.

Suggested fix

Use calendar day comparison instead:

private func formattedDueDate(from reminder: EKReminder) -> String? {
    guard let dueDate = reminder.dueDateComponents?.date else { return nil }
    let calendar = Calendar.current
    let today = calendar.startOfDay(for: Date())
    let dueDay = calendar.startOfDay(for: dueDate)
    let days = calendar.dateComponents([.day], from: today, to: dueDay).day ?? 0

    switch days {
    case ..<0: return "\(abs(days)) day\(abs(days) == 1 ? "" : "s") ago"
    case 0: return "today"
    case 1: return "tomorrow"
    default: return "in \(days) days"
    }
}

This matches how users think about dates: "due in 2 days" means the day after tomorrow, regardless of the specific hour.