Added Network Time Fetching for SimXXX

src/TinyGsmClientSIM800.h

@@ -39,6 +39,11 @@ enum RegStatus {
   REG_UNKNOWN      = 4,
 };
 
+enum DateTime {
+  DATE_FULL = 0,
+  DATE_TIME = 1,
+  DATE_DATE = 2
+};
 
 class TinyGsmSim800
 {
@@ -307,6 +312,13 @@ public:
     if (!testAT()) {
       return false;
     }
+    //Enable Local Time Stamp for getting network time
+    sendAT(GF("+CLTS=1"));
+    if (waitResponse(10000L) != 1) {
+      return false;
+    }
+    sendAT(GF("&W"));
+    waitResponse();
     sendAT(GF("+CFUN=0"));
     if (waitResponse(10000L) != 1) {
       return false;
@@ -719,6 +731,32 @@ public:
     return res;
   }
 
+  /*
+   * Time functions
+   */
+  String getGSMDateTime(DateTime format) {
+    sendAT(GF("+CCLK?"));
+    if (waitResponse(2000L, GF(GSM_NL "+CCLK: \"")) != 1) {
+      return "";
+    }
+    
+    String res;
+
+    switch(format) {
+      case DATE_FULL:
+        res = stream.readStringUntil('"');
+      break;
+      case DATE_TIME:
+        streamSkipUntil(',');
+        res = stream.readStringUntil('"');
+      break;
+      case DATE_DATE:
+        res = stream.readStringUntil(',');
+      break;
+    }
+    return res;
+  }
+
   /*
    * Battery functions
    */