Converting To and From Unix Timestamps with C#

From time to time it's necessary to convert Unix timestamps. These C# methods will do just that and make interacting with Unix easy.

Instead of a date and time, Unix (and Linux) timestamps store a number. This is the number of seconds that have passed since 00:00:00 Coordinated Universal Time (UTC) on Thursday, January 1, 1970. This date and time, known as the Unix epoch, is the starting point for all Unix timestamps. Because leap seconds are not included in Linux timestamps, they aren't comparable to real-time.

When displaying a timestamp, Linux converts the number of seconds into a date and time. This is to help humans understand the numbers. The conversion to a date and time is guided by the location and time zone of the device accessing the number. It also ensures that the day and month are displayed in the relevant language. This conversion process involves several steps, including determining the number of days, hours, minutes, and seconds that have passed since the Unix epoch and then adding these to the Unix epoch date and time.

These two functions will convert a .Net DateTime into a Unix timestamp and vice versa.

public static DateTime ConvertFromUnixTimestamp(ulong timestamp)
{
    DateTime origin = new DateTime(1970, 1, 1, 0, 0, 0, 0);
    return origin.AddSeconds(timestamp);
}

public static double ConvertToUnixTimestamp(DateTime? date = null)
{
    DateTime origin = new DateTime(1970, 1, 1, 0, 0, 0, 0);
    TimeSpan diff = (date ?? DateTime.Now) - origin;
    return Convert.ToDouble(Math.Floor(diff.TotalSeconds));
}

Year 2038 Problem

However, it's crucial to be aware of the limitations of the current implementation of Unix timestamps. On 32-bit data types, 03:14:07 UTC on 19 January 2038 represents an integer's maximum value. The time will roll over one second after this, back to 1970. This is a significant issue, often called the Y2K38 superbug or the Epochalypse, which could impact various data structures and systems.

Any system that uses data structures with 32-bit time representations is doomed to fail. A complete list of these data structures is impossible to compile, but some well-known data structures suffer from the Unix time problem:

• Many file systems utilise only 32 bits to express times in inodes.
• Binary file formats (with time fields of 32 bits)
• Databases with 32-bit time fields
• Database query languages using UNIX_TIMESTAMP()-like commands (such as SQL)

The Unix' time_t' data type represents a point in time. On many platforms, it is a signed 32-bit integer. This means it can hold positive and negative values, with a maximum value of 2,147,483,647. Most operating systems built for 64-bit hardware already use signed 64-bit 'time_t' integers with a new wraparound date more than twenty times bigger than the universe's estimated age: around 292 billion years from now.

The Year 2038 problem may seem daunting, but there are potential solutions. In the C, any change to the time_t data type specification would cause code-compatibility issues. However, changing time_t to an unsigned 32-bit integer, which would expand the range to 2106, could be a viable option. While it may severely impact programmes that save, retrieve, or modify dates before 1970 because negative values represent such dates, it could provide a way forward. In an existing system, increasing the size of the time_t type to 64 bits would result in incompatible structure architecture and function binary interface changes, but it could also be a potential solution.