Relative time-ago parsing in TypeScript

function is(interval: number, cycle: number) {
  return cycle >= interval ? Math.floor(cycle / interval) : 0
}
 
export function getTimeAgo(time: string | number | Date, now = Date.now()): string {
  if (typeof time === 'string' || time instanceof Date) {
    time = new Date(time).getTime()
  }
 
  let secs = (now - time) / 1000
  let mins = is(60, secs)
  let hours = is(60, mins)
  let days = is(24, hours)
  let weeks = is(7, days)
  let months = is(30, days)
  let years = is(12, months)
 
  let amt = years
  let cycle = 'year'
 
  if (secs <= 1) {
    return 'just now'
  }
  if (years > 0) {
    amt = years
    cycle = 'year'
  } else if (months > 0) {
    amt = months
    cycle = 'month'
  } else if (weeks > 0) {
    amt = weeks
    cycle = 'week'
  } else if (days > 0) {
    amt = days
    cycle = 'day'
  } else if (hours > 0) {
    amt = hours
    cycle = 'hour'
  } else if (mins > 0) {
    amt = mins
    cycle = 'minute'
  } else if (secs > 0) {
    amt = secs
    cycle = 'second'
  }
 
  let v = Math.floor(amt)
 
  return `${v === 1 ? (amt === hours ? 'an' : 'a') : v} ${cycle}${v > 1 ? 's' : ''} ago`
}

const MARCH_10_2025 = new Date('2025-03-10').getTime()
 
getTimeAgo(MARCH_10_2025, MARCH_10_2025) // 'just now'
getTimeAgo('2025-03-08', MARCH_10_2025) // '2 days ago'
getTimeAgo('2025-03-02', MARCH_10_2025) // 'a week ago'