Epoch Converter for TypeScript Developers

// Type-safe epoch utilities
type UnixTimestamp = number & { readonly _brand: 'UnixTimestamp' };

function toEpoch(date: Date): UnixTimestamp {
  return Math.floor(date.getTime() / 1000) as UnixTimestamp;
}

function fromEpoch(epoch: UnixTimestamp): Date {
  return new Date(epoch * 1000);
}

const now = toEpoch(new Date());
const date = fromEpoch(1700000000 as UnixTimestamp);
console.log(date.toISOString()); // 2023-11-14T22:13:20.000Z

// Relative time formatter
const rtf = new Intl.RelativeTimeFormat('en', { numeric: 'auto' });
const diffDays = Math.round((date.getTime() - Date.now()) / 86400000);
console.log(rtf.format(diffDays, 'day'));