First we have to create a class for our timer job which inherits SPTimerJobDefinition, build it and deploy it.

public class TakanaTimer : SPJobDefinition
{
	public TakanaTimer(){}
	public TakanaTimer(string jobName, SPService service,
		SPServer server, SPJobLockType targetType)
		: base(jobName, service, server, targetType) { }

	public TakanaTimer(string jobName, SPWebApplication webapp)
		: base(jobName, webapp, null, SPJobLockType.ContentDatabase)
	{
		Title = jobName;
	}
	public override void Execute(Guid contentDbId)
	{
		Log.Info("Running Takana Timer");
	}
}

There is a powershell example for this, but it has not been updated since MOSS.