以下详细说明暂以英文提供。
What a Unix timestamp measures
A Unix timestamp is simply the number of seconds elapsed since 00:00:00 UTC on January 1, 1970 — the "epoch" — not counting leap seconds. Because it is a single plain number, it is the standard way programs store points in time: sorting, comparing, and arithmetic all become trivial, and no time zone is embedded in the value. The same instant reads as afternoon in New York and midnight the next day in Tokyo, but the timestamp itself never changes.
Seconds versus milliseconds
Most systems count seconds, which produce ten digits for dates in the current era (1700000000 falls in November 2023). JavaScript and some Java libraries instead use thirteen-digit milliseconds, so a value like 1700000000000 is one thousand times larger. This converter auto-detects the longer form: any timestamp of twelve or more digits is treated as milliseconds and converted. If a converted date lands in January 1970, you are probably looking at the wrong unit.
中国本地参考
日常计算时值得知道的中国本地规则：
- 计量的单位习惯: 住房面积用平方米，土地常用亩（1 亩 ≈ 666.7 平方米）；里程用公里，油耗用 L/100km。
- 日期与数字格式: 日期写作 2026年10月13日（年-月-日）；大数习惯用万、亿（1 万 = 10,000，1 亿 = 100,000,000）。
- 法定节假日: 全年法定节假日 11 天，春节与国庆为长假；调休安排每年由国务院办公厅发布。
- 速度与限速: 高速公路最高限速 120 km/h，城市快速路多为 80 km/h，均以公里每小时计。
- 鞋服尺码: 鞋码用中国码（毫米制），服装常用 155/80A 这类身高围度组合，与欧美码不同。
数据核对：2026 年 10 月
常见问题
Do timestamps handle time zones?
By design, no. A timestamp is always relative to UTC, which is why it is unambiguous. The date shown here is the UTC reading; convert to a local zone only when displaying it to people.
Why does my timestamp show a date in 1970?
You are most likely mixing units — a seconds value interpreted as milliseconds gives dates a thousand times earlier. Values of ten digits are seconds; thirteen digits are milliseconds, which this tool converts automatically.
What happens at 2038?
Older 32-bit systems run out of room on January 19, 2038, when the seconds counter overflows. Modern 64-bit systems, including everything that runs this page, are unaffected and good for hundreds of billions of years.