The parameters I used were global variables, as pointed out previously, so I guess I don't need to pass them so I removed them.
Now I am getting these errors:
My_60_Pixel_Ring_Clock_Version_3:140:41: error: cannot convert 'String' to 'char' in initialization
char theyear = dayStamp.substring(0, 4);
^
My_60_Pixel_Ring_Clock_Version_3:141:42: error: cannot convert 'String' to 'char' in initialization
char themonth = dayStamp.substring(5, 7);
^
My_60_Pixel_Ring_Clock_Version_3:142:41: error: cannot convert 'String' to 'char' in initialization
char theday = dayStamp.substring(9, 11);
^
My_60_Pixel_Ring_Clock_Version_3:143:32: error: no match for call to '(String) (int, int)'
char thehour = timeStamp(0, 2);
^
My_60_Pixel_Ring_Clock_Version_3:144:44: error: cannot convert 'String' to 'char' in initialization
char theminute = timeStamp.substring(3, 5);
^
My_60_Pixel_Ring_Clock_Version_3:145:44: error: cannot convert 'String' to 'char' in initialization
char thesecond = timeStamp.substring(6, 8);
^
My_60_Pixel_Ring_Clock_Version_3:149:21: error: request for member 'toint' in 'theyear', which is of non-class type 'char'
yearval = theyear.toint();
^
My_60_Pixel_Ring_Clock_Version_3:150:23: error: request for member 'toint' in 'themonth', which is of non-class type 'char'
monthval = themonth.toint();
^
My_60_Pixel_Ring_Clock_Version_3:151:19: error: request for member 'toint' in 'theday', which is of non-class type 'char'
dayval = theday.toint();
^
My_60_Pixel_Ring_Clock_Version_3:154:21: error: request for member 'toint' in 'thehour', which is of non-class type 'char'
hourval = thehour.toint();
^
My_60_Pixel_Ring_Clock_Version_3:155:25: error: request for member 'toint' in 'theminute', which is of non-class type 'char'
minuteval = theminute.toint();
^
My_60_Pixel_Ring_Clock_Version_3:156:25: error: request for member 'toint' in 'thesecond', which is of non-class type 'char'
secondval = thesecond.toint();
^
exit status 1
cannot convert 'String' to 'char' in initialization
I would guess that I am not using the proper way to convert the string to an integer. The formatted date and time comes in a string like 2019-03-28T16:00:13Z. What I am trying to do is to separate the year, month, day, hour, minute and second using substrings and then converting each one to an integer.