Complete Guide to Timestamps: Principles, Conversion, and Application Scenarios

Timestamp is a common way to represent date and time in computers. It is simple, precise, and easy to process. This article explores the principles of timestamps, various conversion methods, and practical application scenarios in depth.

I. Timestamp Principles

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

Historical Background

The Unix epoch was chosen 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' — on January 19, 2038, 32-bit timestamps will overflow. Modern systems generally use 64-bit integers, which can represent time up to about 58 billion years from now.

Precision Description

Timestamp precision is divided into second-level and millisecond-level. Second-level timestamps (10 digits) have second precision, suitable for scenarios that don't require millisecond precision; millisecond-level timestamps (13 digits) have millisecond precision, suitable for scenarios requiring millisecond accuracy, such as real-time data processing, logging, etc.

II. Timestamp Operations in JavaScript

2.1 Getting 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

III. 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;

IV. 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 if cache has expired:

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);

V. Advanced Techniques

5.1 Timezone Handling Explained

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 Handling

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

VI. Comparison of Date/Time Libraries

Choosing the right date processing library:

VII. Using TudoSi Tools for Timestamp Processing

TudoSi Tools provides convenient timestamp conversion features:

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

Use Timestamp Converter Now

VIII. Summary

Timestamp is a fundamental concept for handling date and time. Mastering its principles and conversion methods is crucial for development work. TudoSi Tools' timestamp conversion feature can help you quickly complete various time-related tasks.