Math.floor(Date.now() / 1000)  // seconds
Date.now()                     // milliseconds

import time
int(time.time())               # seconds
time.time_ns() // 1_000_000    # milliseconds

date +%s                       # seconds
date +%s%3N                    # milliseconds (GNU date)

import "time"
time.Now().Unix()              // seconds
time.Now().UnixMilli()         // milliseconds

System.currentTimeMillis() / 1000L  // seconds
System.currentTimeMillis()          // milliseconds
Instant.now().getEpochSecond()      // Java 8+

time()                         // seconds
round(microtime(true) * 1000)  // milliseconds

EXTRACT(EPOCH FROM NOW())::bigint
-- or
SELECT FLOOR(EXTRACT(EPOCH FROM NOW()));

SELECT UNIX_TIMESTAMP();
SELECT UNIX_TIMESTAMP(NOW());

Time.now.to_i                  # seconds
Time.now.to_f.round(3)         # milliseconds

use std::time::{SystemTime, UNIX_EPOCH};
SystemTime::now()
  .duration_since(UNIX_EPOCH)
  .unwrap().as_secs()           // seconds

DateTimeOffset.UtcNow.ToUnixTimeSeconds()      // seconds
DateTimeOffset.UtcNow.ToUnixTimeMilliseconds() // ms

Int(Date().timeIntervalSince1970)        // seconds
Int(Date().timeIntervalSince1970 * 1000) // ms