A pattern to implement a scheduler in Unity DOTS.

ScheduleSystem.cs

using Unity.Collections;
using Unity.Entities;
using Unity.Jobs;

namespace PatternsOfDots
{
    /// <summary>
    /// Add a WaitForSeconds component to your entity with a delay parameter.
    /// The ScheduleSystem will then wait that many seconds before removing
    /// the component, and add a Ready tag component. You can then process
    /// the Ready component in your own systems.
    /// </summary>
    public struct WaitForSeconds : IComponentData
    {
        public float time;

        public WaitForSeconds(float delay) => this.time = UnityEngine.Time.time + delay;
    }

    public struct Ready : IComponentData { }

    public class ScheduleSystem : ComponentSystem
    {
        protected override void OnUpdate()
        {
            var now = UnityEngine.Time.time;
            Entities.ForEach<WaitForSeconds>((Entity e, ref WaitForSeconds s) =>
            {
                if (s.time <= now)
                {
                    PostUpdateCommands.RemoveComponent<WaitForSeconds>(e);
                    PostUpdateCommands.AddComponent<Ready>(e, new Ready());
                }
            });
        }
    }
}