Unix timestamp converter

// Current Unix time in seconds
Math.floor(Date.now() / 1000)

// Unix time to date
new Date(1000425600 * 1000).toISOString()

// Date to Unix time
Date.parse("2001-09-14T00:00:00Z") / 1000

from datetime import datetime, timezone
import time

# Current Unix time in seconds
int(time.time())

# Unix time to date
datetime.fromtimestamp(1000425600, tz=timezone.utc).isoformat()

# Date to Unix time
int(datetime.fromisoformat("2001-09-14T00:00:00+00:00").timestamp())

// Current Unix time in seconds
time.Now().Unix()

// Unix time to date
time.Unix(1000425600, 0).UTC().Format(time.RFC3339)

// Date to Unix time
t, _ := time.Parse(time.RFC3339, "2001-09-14T00:00:00Z")
t.Unix()

// Current Unix time in seconds
Instant.now().getEpochSecond()

// Unix time to date
Instant.ofEpochSecond(1000425600L).toString()

// Date to Unix time
Instant.parse("2001-09-14T00:00:00Z").getEpochSecond()

// Current Unix time in seconds
DateTimeOffset.UtcNow.ToUnixTimeSeconds()

// Unix time to date
DateTimeOffset.FromUnixTimeSeconds(1000425600).ToString("o")

// Date to Unix time
DateTimeOffset.Parse("2001-09-14T00:00:00Z").ToUnixTimeSeconds()

// Current Unix time in seconds (std)
SystemTime::now().duration_since(UNIX_EPOCH).unwrap().as_secs()

// Unix time to date (chrono 0.4.31 or later)
DateTime::from_timestamp(1000425600, 0).unwrap().to_rfc3339()

// Date to Unix time (chrono)
DateTime::parse_from_rfc3339("2001-09-14T00:00:00Z").unwrap().timestamp()

// Current Unix time in seconds
time();

// Unix time to date
gmdate('c', 1000425600);

// Date to Unix time
strtotime('2001-09-14T00:00:00Z');

require "time"

# Current Unix time in seconds
Time.now.to_i

# Unix time to date
Time.at(1000425600).utc.iso8601

# Date to Unix time
Time.iso8601("2001-09-14T00:00:00Z").to_i

-- Current Unix time in seconds
SELECT floor(extract(epoch FROM now()))::bigint;

-- Unix time to date
SELECT to_timestamp(1000425600) AT TIME ZONE 'UTC';

-- Date to Unix time
SELECT extract(epoch FROM timestamptz '2001-09-14T00:00:00Z')::bigint;

-- FROM_UNIXTIME and UNIX_TIMESTAMP use the session time zone
SET time_zone = '+00:00';

-- Current Unix time in seconds
SELECT UNIX_TIMESTAMP();

-- Unix time to date
SELECT FROM_UNIXTIME(1000425600);

-- Date to Unix time
SELECT UNIX_TIMESTAMP('2001-09-14 00:00:00');

-- unixepoch() needs SQLite 3.38 or later
-- Current Unix time in seconds
SELECT unixepoch();

-- Unix time to date
SELECT datetime(1000425600, 'unixepoch');

-- Date to Unix time
SELECT unixepoch('2001-09-14 00:00:00');

# Current Unix time in seconds
date +%s

# Unix time to date
date -u -d @1000425600 +%Y-%m-%dT%H:%M:%SZ

# Date to Unix time
date -u -d "2001-09-14T00:00:00Z" +%s

# Current Unix time in seconds
date +%s

# Unix time to date
date -u -r 1000425600 +%Y-%m-%dT%H:%M:%SZ

# Date to Unix time
date -u -j -f "%Y-%m-%dT%H:%M:%SZ" "2001-09-14T00:00:00Z" +%s

# Current Unix time in seconds
[DateTimeOffset]::UtcNow.ToUnixTimeSeconds()

# Unix time to date
[DateTimeOffset]::FromUnixTimeSeconds(1000425600).UtcDateTime

# Date to Unix time
[DateTimeOffset]::Parse("2001-09-14T00:00:00Z").ToUnixTimeSeconds()

Unix time to date (UTC), with the cell formatted as a date and time
=1000425600/86400+DATE(1970,1,1)

Date in A1 (UTC) to Unix time
=(A1-DATE(1970,1,1))*86400

Excel has no time zones: NOW() is local time, so subtract your UTC offset
=(NOW()-DATE(1970,1,1))*86400