Error:

o.reload WipeDates
[CSharp] Started Oxide.Compiler v successfully
WipeDates was compiled successfully in 1312ms
Failed to initialize plugin 'WipeDates v1.0.3' (InvalidOperationException: Sequence contains no elements)
  at System.Linq.Enumerable.First[TSource] (System.Collections.Generic.IEnumerable`1[T] source) [0x00010] in <c4112faf3ded44a7b1e0b815a3296c25>:0 
  at Oxide.Plugins.WipeDates.calculate_wipe_dates () [0x000a5] in <3fd4412343404a11ba4a594920db63d5>:0 
  at Oxide.Plugins.WipeDates.Init () [0x00011] in <3fd4412343404a11ba4a594920db63d5>:0 
  at Oxide.Plugins.WipeDates.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x00038] in <3fd4412343404a11ba4a594920db63d5>:0 
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <87ce9ac9776a48658bc55eae6debe38b>:0 
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <18d4f19bbc844191b11ed9e69284d09b>:0 
  at Oxide.Core.Plugins.CSPlugin.HandleAddedToManager (Oxide.Core.Plugins.PluginManager manager) [0x00043] in <18d4f19bbc844191b11ed9e69284d09b>:0 
Unloaded plugin Wipe Dates v1.0.3 by Freakyy
No previous version to rollback plugin: WipeDates
Shutting down compiler because idle shutdown
Compiler shutdown completed

Fix:

private void calculate_wipe_dates()
{
    if (All_Wipe_Dates.Count == 0)
    {
        PrintError("Missing entries in config file. (All_Wipe_Dates)");
        return;
    }

    List<string> Past_Dates = All_Wipe_Dates.Where(x => Convert.ToDateTime(x) < DateTime.Now).OrderByDescending(x => x).ToList();
    List<string> Future_Dates = All_Wipe_Dates.Where(x => Convert.ToDateTime(x) > DateTime.Now).ToList();

    if (Past_Dates.Count > 0)
    {
        Last_Wipe = Convert.ToDateTime(Past_Dates.First()).ToString(_Settings.Date_Format);
    }
    else
    {
        Last_Wipe = "No previous wipes found";
    }

    if (Future_Dates.Count > 0)
    {
        Future_Dates.Sort();
        Next_Wipe = Convert.ToDateTime(Future_Dates.First()).ToString(_Settings.Date_Format);
    }
    else
    {
        Next_Wipe = "No upcoming wipes found";
    }
}

Let me know if this fixes your problem if your having the same issue.