Use VB.NET indexing for months and days ;-)

Author: nblumhardt

src/Serilog.Sinks.File/Sinks/File/RollingIntervalExtensions.cs

@@ -46,9 +46,9 @@ public static string GetFormat(this RollingInterval interval)
                 case RollingInterval.Infinite:
                     return null;
                 case RollingInterval.Year:
-                    return new DateTime(instant.Year, 0, 0, 0, 0, 0, instant.Kind);
+                    return new DateTime(instant.Year, 1, 1, 0, 0, 0, instant.Kind);
                 case RollingInterval.Month:
-                    return new DateTime(instant.Year, instant.Month, 0, 0, 0, 0, instant.Kind);
+                    return new DateTime(instant.Year, instant.Month, 1, 0, 0, 0, instant.Kind);
                 case RollingInterval.Day:
                     return new DateTime(instant.Year, instant.Month, instant.Day, 0, 0, 0, instant.Kind);
                 case RollingInterval.Hour: