Timestamps are a common way to represent dates and times in computing. They are simple, precise and easy to handle. This article explores timestamp principles, conversion methods and practical applications.

1. Timestamp Principles

A timestamp is the number of seconds or milliseconds since January 1, 1970, 00:00:00 UTC (Unix epoch). The choice of the Unix epoch was not accidental; it is the birth time of the Unix operating system, and this choice makes timestamps a universal time representation across platforms and languages.

Historical Background

The choice of the Unix epoch was made by Unix developers Dennis Ritchie and Ken Thompson in 1971. Initially, timestamps were represented using 32-bit integers, which led to the famous 'Year 2038 problem' — by January 19, 2038, 32-bit timestamps would overflow. Modern systems generally use 64-bit integers, which can represent times up to approximately 58 billion years from now.

Precision Explanation

Timestamp precision is divided into second-level and millisecond-level. Second-level timestamps (10-digit numbers) have second precision, suitable for scenarios that do not require millisecond-level precision; millisecond-level timestamps (13-digit numbers) have millisecond precision, suitable for scenarios that require precision to the millisecond, such as real-time data processing, logging, etc.

2. Timestamp Operations in JavaScript

2.1 Get Current Timestamp

// 获取毫秒时间戳
const timestampMs = Date.now();
// 1715068800000

// 使用 Date 对象
const timestampMs2 = new Date().getTime();
// 1715068800000

// 获取秒时间戳
const timestampSec = Math.floor(Date.now() / 1000);
// 1715068800

2.2 Timestamp to Date Object

const timestamp = 1715068800000;
const date = new Date(timestamp);

console.log(date.getFullYear());    // 2026
console.log(date.getMonth() + 1);   // 5 (月份从0开始)
console.log(date.getDate());        // 6
console.log(date.getHours());       // 0
console.log(date.getMinutes());     // 0

2.3 Timestamp Formatting

function formatTimestamp(timestamp, format = 'YYYY-MM-DD HH:mm:ss') {
  const date = new Date(timestamp);
  const pad = (n) => n.toString().padStart(2, '0');
  
  return format
    .replace('YYYY', date.getFullYear())
    .replace('MM', pad(date.getMonth() + 1))
    .replace('DD', pad(date.getDate()))
    .replace('HH', pad(date.getHours()))
    .replace('mm', pad(date.getMinutes()))
    .replace('ss', pad(date.getSeconds()));
}

console.log(formatTimestamp(1715068800000));
// 2026-05-06 00:00:00

3. Timestamp Conversion

3.1 Date String to Timestamp

const dateStr = '2026-05-06';
const timestamp = new Date(dateStr).getTime();
// 1715068800000

// 指定时区
const timestampUTC = new Date('2026-05-06T00:00:00Z').getTime();

3.2 Timezone Conversion

// 获取 UTC 时间戳
const utcDate = new Date(Date.UTC(2026, 4, 6));
const utcTimestamp = utcDate.getTime();

// 本地时间转 UTC
const localDate = new Date();
const utcTimestamp2 = localDate.getTime() - localDate.getTimezoneOffset() * 60000;

4. Common Application Scenarios

4.1 Database Storage

Most databases support timestamp types:

// MySQL
CREATE TABLE events (
  id INT PRIMARY KEY,
  created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

// MongoDB
{
  "_id": ObjectId(),
  "createdAt": ISODate("2026-05-06T00:00:00Z")
}

4.2 Cache Control

Using timestamps to determine cache expiration:

const cache = {
  data: null,
  timestamp: 0,
  ttl: 3600000 // 1小时
};

function getData() {
  const now = Date.now();
  if (cache.data && now - cache.timestamp < cache.ttl) {
    return cache.data;
  }
  // 重新获取数据
  cache.data = fetchData();
  cache.timestamp = now;
  return cache.data;
}

4.3 Data Sorting

Sorting data by time:

const posts = [
  { id: 1, createdAt: 1715068800000 },
  { id: 2, createdAt: 1714982400000 },
  { id: 3, createdAt: 1715155200000 }
];

// 按时间降序排序
posts.sort((a, b) => b.createdAt - a.createdAt);

5. Advanced Techniques

5.1 Timezone Handling Deep Dive

Timezone handling in JavaScript:

// 获取当前时区偏移（分钟）
const offset = new Date().getTimezoneOffset();
// 中国时区：-480（UTC+8）

// 格式化不同时区的时间
function formatTimezone(date, timezone) {
  return date.toLocaleString('zh-CN', {
    timeZone: timezone,
    year: 'numeric',
    month: '2-digit',
    day: '2-digit',
    hour: '2-digit',
    minute: '2-digit',
    second: '2-digit'
  });
}

console.log(formatTimezone(new Date(), 'UTC'));
console.log(formatTimezone(new Date(), 'Asia/Shanghai'));
console.log(formatTimezone(new Date(), 'America/New_York'));

5.2 Daylight Saving Time

Detecting and handling daylight saving time:

function isDaylightSavingTime(date, timezone = 'America/New_York') {
  const jan = new Date(date.getFullYear(), 0, 1);
  const jul = new Date(date.getFullYear(), 6, 1);
  const stdTimezoneOffset = Math.max(jan.getTimezoneOffset(), jul.getTimezoneOffset());
  return date.getTimezoneOffset() < stdTimezoneOffset;
}

console.log(isDaylightSavingTime(new Date()));
// 输出当前是否处于夏令时

5.3 Relative Time Formatting

Converting timestamps to relative time descriptions:

function formatRelativeTime(timestamp) {
  const now = Date.now();
  const diff = now - timestamp;
  
  const minute = 60 * 1000;
  const hour = 60 * minute;
  const day = 24 * hour;
  const week = 7 * day;
  const month = 30 * day;
  const year = 365 * day;
  
  if (diff < minute) return '刚刚';
  if (diff < hour) return `${Math.floor(diff / minute)}分钟前`;
  if (diff < day) return `${Math.floor(diff / hour)}小时前`;
  if (diff < week) return `${Math.floor(diff / day)}天前`;
  if (diff < month) return `${Math.floor(diff / week)}周前`;
  if (diff < year) return `${Math.floor(diff / month)}月前`;
  return `${Math.floor(diff / year)}年前`;
}

console.log(formatRelativeTime(Date.now() - 3600000)); // 1小时前

5.4 Common Issues and Debugging

6. Date/time Library Comparison

Choose the right date handling library:

7. Using Tudousi Tools for Timestamps

Tudousi Tools provides convenient timestamp conversion features:

• Supports second, millisecond, microsecond timestamp conversion
• Supports multiple date format outputs
• Supports timezone conversion
• Real-time preview of conversion results

Use Timestamp Tool Now

8. Summary

Timestamps are fundamental concepts for handling dates and times. Mastering their principles and conversion methods is crucial for development work. Tudousi Tools' timestamp conversion feature helps you quickly complete various time-related tasks.