Konwerter Znaczników Czasu

A Unix timestamp is an integer representing the number of seconds elapsed since the Unix epoch — midnight on January 1, 1970, Coordinated Universal Time (UTC). It was standardized alongside the C programming language and the early Unix operating system in the early 1970s and has since become the universal currency for storing and transmitting time in software. Because it is simply a number with no timezone attached, it is unambiguous: the same integer means exactly the same instant everywhere on Earth, which makes it ideal for databases, APIs, log files, and inter-system communication. Most programming languages provide built-in functions to produce or consume Unix timestamps — JavaScript uses Date.now(), Python uses time.time(), and Go uses time.Now().Unix(). The format is deliberately lightweight: a 32-bit signed integer can represent dates from 1901 to 2038, while 64-bit variants extend that range by billions of years, eliminating the Year 2038 problem that affects older systems. This converter processes everything locally using your browser's built-in JavaScript Date object — no data leaves your device. When you see a Unix timestamp in a server log or API response and need to know what moment it represents in plain language, this tool gives you an instant answer. Practical tip: if you are debugging an API and unsure whether a timestamp is seconds or milliseconds, check whether the value has 10 digits (seconds) or 13 digits (milliseconds) — that is the quickest way to tell which format you are dealing with.

To convert a Unix timestamp to a human-readable date, paste the integer into the timestamp field and the tool immediately displays the equivalent date and time in both UTC and your local timezone using JavaScript's Date constructor internally. To go in the other direction, type or pick a human-readable date and the tool computes the corresponding Unix timestamp in seconds and milliseconds. The conversion relies entirely on the ECMAScript Date object built into every modern browser — no external libraries or server calls are involved, so your data never leaves your device. Under the hood, the Date constructor accepts millisecond-epoch values directly, so seconds-based timestamps are multiplied by 1000 before being passed in; the tool handles this automatically depending on whether it detects a 10-digit or 13-digit input. The resulting human-readable string is produced using Intl.DateTimeFormat, which respects your operating system's locale and timezone settings and renders month names, day/month ordering, and AM/PM notation in a way that is familiar to you. You can also enter ISO 8601 strings like 2025-06-15T14:30:00Z and convert them forward to a Unix timestamp in one click, which is useful when constructing API query parameters or writing cron-job schedules. Practical tip: always verify whether the timestamp you are working with is in seconds or milliseconds before converting — pasting a milliseconds value into a seconds field will produce a date far in the future, around the year 2001 if the value is from late 2024.

The difference reflects the unit of measurement: 10-digit timestamps count whole seconds since the Unix epoch, while 13-digit timestamps count milliseconds. A 10-digit value like 1716000000 represents a specific second in May 2025, whereas a 13-digit value like 1716000000000 represents that same second expressed in milliseconds. The seconds format originated in early Unix and C code where time_t was a 32-bit integer; milliseconds became common as JavaScript's Date.now() and many web APIs returned finer-grained values. Some platforms go even further: 16-digit timestamps use microseconds and 19-digit timestamps use nanoseconds, which you encounter in high-frequency trading systems, database engines like PostgreSQL's TIMESTAMPTZ, and hardware event logs. The converter auto-detects whether your input is seconds or milliseconds by checking the magnitude of the number — values above roughly 9999999999 are treated as milliseconds. Everything runs locally in your browser using JavaScript arithmetic, so no data is transmitted to any server. It is worth noting that 32-bit seconds timestamps will overflow at 2147483647, corresponding to January 19, 2038 — a known issue called the Year 2038 problem. Most modern systems have migrated to 64-bit integers, which can represent times billions of years into the future. Practical tip: when writing code that stores or reads timestamps, document the unit explicitly in variable names or database column names — for example, created_at_ms versus created_at_s — to prevent subtle bugs when integrating with other services.

Yes — the converter handles timezones correctly by anchoring all calculations to UTC and then applying your local timezone offset only for display purposes. Unix timestamps are inherently UTC values; they represent a single universal instant with no timezone baked in. When you convert a timestamp to a human-readable date, the tool shows both the UTC representation and the local time in your browser's detected timezone, which is pulled from the Intl.DateTimeFormat API using your operating system settings. If you want to see the same moment in a different timezone, you can select a target timezone from the dropdown and the tool applies the appropriate UTC offset — including daylight saving time rules maintained in the IANA Time Zone Database that modern browsers bundle. The conversion back from a local date to a Unix timestamp is equally careful: the tool treats your typed date as local time, resolves the UTC offset for that specific date and time (accounting for DST transitions), and computes the correct epoch value. All of this runs entirely in your browser — no data leaves your device. One subtle edge case is ambiguous local times that occur during the clock-backward transition of daylight saving time: for example, 1:30 AM can occur twice on the night clocks fall back. The converter defaults to the first occurrence (standard time) in such cases. Practical tip: if you are comparing timestamps from servers in different regions, always convert to UTC first to avoid off-by-one-hour errors caused by DST differences.