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Convert ISO8601 UTC string to UNIX timestamp and vice versa in Javascript
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const epoch = 1970 | |
const dayInSeconds = 86400 | |
const hourInSeconds = 3600 | |
const minuteInSeconds = 60 | |
const dayInHours = 24 | |
const toInt = v => parseInt(v) | |
const isLeap = v => ((v % 4 == 0) && (v % 100 != 0)) || (v % 400 == 0) | |
const pad = (v, n = 2) => v.toString().padStart(n, '0') | |
function ts2iso(ts) { | |
const seconds = ts % minuteInSeconds | |
const minutes = parseInt(ts / minuteInSeconds) % minuteInSeconds | |
const hours = parseInt(ts / hourInSeconds) % dayInHours | |
const daysInMonths = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31] | |
let days = parseInt(ts / dayInSeconds) + 1 | |
let years = epoch | |
let months = 1 | |
while (days > 365) { | |
if (isLeap(years)) { | |
if (days === 366) break | |
days -= 366 | |
} else { | |
days -= 365 | |
} | |
years++ | |
} | |
if (isLeap(years)) daysInMonths[1] = 29 | |
while (days > daysInMonths[months - 1]) { | |
days -= daysInMonths[months - 1] | |
months++ | |
} | |
const date = `${pad(years, 4)}-${pad(months)}-${pad(days)}` | |
const time = `${pad(hours)}:${pad(minutes)}:${pad(seconds)}` | |
return date + 'T' + time + 'Z' | |
} | |
function iso2ts(iso) { | |
const [date, time] = iso.split('T') | |
const [year, month, day] = date.split('-').map(toInt) | |
const [hour, minute, second] = time.replace('Z', '').split(':').map(toInt) | |
const daysInMonths = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31] | |
let ts = 0 | |
for (let i = epoch; i < year; i++) { | |
ts += (isLeap(i) ? 366 : 365) * dayInSeconds | |
} | |
if (isLeap(year)) daysInMonths[1] = 29 | |
for (let i = 0; i < month - 1; i++) { | |
ts += daysInMonths[i] * dayInSeconds | |
} | |
ts += (day - 1) * dayInSeconds | |
ts += hour * hourInSeconds | |
ts += minute * minuteInSeconds | |
ts += second | |
return ts | |
} | |
const tests = { | |
"10": "1970-01-01T00:00:10Z", | |
"63072000": "1972-01-01T00:00:00Z", | |
"315532800": "1980-01-01T00:00:00Z", | |
"647135999": "1990-07-04T23:59:59Z", | |
"951825600": "2000-02-29T12:00:00Z", | |
"1273903628": "2010-05-15T06:07:08Z", | |
"1609459199": "2020-12-31T23:59:59Z", | |
"1709164800": "2024-02-29T00:00:00Z", | |
"1909074600": "2030-06-30T18:30:00Z", | |
"2214172862": "2040-03-01T00:01:02Z" | |
} | |
Object.entries(tests).sort((a, b) => a[0] - b[0]).forEach(([ts, iso]) => { | |
ts = parseInt(ts) | |
const iso2 = ts2iso(ts) | |
const ts2 = iso2ts(iso) | |
if (iso2 !== iso) console.log('ts2iso mismatch ', ts, iso, iso2) | |
if (ts2 !== ts) console.log('iso2ts mismatch ', iso, ts, ts2) | |
}) | |
console.log('done') |
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