Tracking time in Unity

Stopwatch.cs

/// <summary>
/// Keeps track of elapsed time, and is able to pause, resume & seek.
/// It's bound to Time.time, so time scaling will affect this.
/// </summary>
public struct Stopwatch
{
	/// <summary>
	/// How much time has passed for this stopwatch
	/// </summary>
	public float Elapsed => Time.time - epoch - (pausedEpoch > 0f ? (Time.time - pausedEpoch) : 0f);

	private float epoch;

	private float pausedEpoch;

	/// <summary>
	/// Create a new stopwatch. If you don't use this method for construction the stopwatch will
	/// be counting from the start of the game.
	/// </summary>
	/// <returns></returns>
	public static Stopwatch Create() => new Stopwatch
	{
		epoch = Time.time,
		pausedEpoch = 0f
	};

	/// <summary>
	/// Pause the stopwatch. Time will not progress for it until it's resumed
	/// </summary>
	public void Pause()
	{
		if (pausedEpoch > 0f)
			epoch += Time.time - pausedEpoch;
		pausedEpoch = Time.time;
	}

	/// <summary>
	/// Make time progress for this stopwatch again
	/// </summary>
	public void Resume()
	{
		if (pausedEpoch > 0f)
			epoch += Time.time - pausedEpoch;
		pausedEpoch = 0f;
	}

	/// <summary>
	/// Start counting from zero or optionally a set point
	/// </summary>
	public void Reset(float startFrom = 0f)
	{
		epoch = Time.time - Mathf.Max(0f, startFrom);
		pausedEpoch = pausedEpoch > 0f ? Time.time : 0f;
	}

	/// <summary>
	/// Modify elapsed by this amount. The resulting time will not become negative
	/// </summary>
	/// <param name="amount"></param>
	public void Seek(float amount)
	{
		epoch -= amount;
		epoch += Elapsed < 0 ? Elapsed : 0;
	}
}