Error: String was not recognized as a valid DateTime for windows service in ASP.Net

referring

https://www.aspsnippets.com/Articles/Automatically-send-emails-daily-at-specific-time-using-Windows-Service-in-C-and-VBNet.aspx

i am geeting error

Service Error on: 18/05/2017 10:49:22 AM String was not recognized as a valid DateTime. at System.DateTimeParse.Parse(String s, DateTimeFormatInfo dtfi, DateTimeStyles styles) at System.DateTime.Parse(String s)