fix SDate.Now() crashing during new-game intro (#369)

3 files changed, 41 insertions, 18 deletions

diff --git a/docs/release-notes.md b/docs/release-notes.md
index fd59bd07..64588744 100644
--- a/docs/release-notes.md
+++ b/docs/release-notes.md
@@ -29,6 +29,7 @@ For mod developers:
 * Removed support for mods with no `Name`, `Version`, or `UniqueID` in their manifest.
 * Removed support for mods with a non-unique `UniqueID` value in their manifest.
 * Removed access to SMAPI internals through the reflection helper, to discourage fragile mods.
+* Fixed `SDate.Now()` crashing when called during the new-game intro.
 * Fixed `TimeEvents.AfterDayStarted` being raised during the new-game intro.
 * Fixed SMAPI allowing map tilesheets with absolute or directory-climbing paths. These are now rejected even if the path exists, to avoid problems when players install the mod.
 
diff --git a/src/SMAPI.Tests/Utilities/SDateTests.cs b/src/SMAPI.Tests/Utilities/SDateTests.cs
index 25acbaf3..86a0d3d0 100644
--- a/src/SMAPI.Tests/Utilities/SDateTests.cs
+++ b/src/SMAPI.Tests/Utilities/SDateTests.cs
@@ -69,6 +69,8 @@ namespace StardewModdingAPI.Tests.Utilities
         [TestCase(01, "Spring", 1)] // seasons are case-sensitive
         [TestCase(01, "springs", 1)] // invalid season name
         [TestCase(-1, "spring", 1)] // day < 0
+        [TestCase(0, "spring", 1)] // day zero
+        [TestCase(0, "spring", 2)] // day zero
         [TestCase(29, "spring", 1)] // day > 28
         [TestCase(01, "spring", -1)] // year < 1
         [TestCase(01, "spring", 0)] // year < 1
diff --git a/src/SMAPI/Utilities/SDate.cs b/src/SMAPI/Utilities/SDate.cs
index 326d7fc7..2630731a 100644
--- a/src/SMAPI/Utilities/SDate.cs
+++ b/src/SMAPI/Utilities/SDate.cs
@@ -52,28 +52,12 @@ namespace StardewModdingAPI.Utilities
         /// <param name="year">The year.</param>
         /// <exception cref="ArgumentException">One of the arguments has an invalid value (like day 35).</exception>
         public SDate(int day, string season, int year)
-        {
-            // validate
-            if (season == null)
-                throw new ArgumentNullException(nameof(season));
-            if (!this.Seasons.Contains(season))
-                throw new ArgumentException($"Unknown season '{season}', must be one of [{string.Join(", ", this.Seasons)}].");
-            if (day < 1 || day > this.DaysInSeason)
-                throw new ArgumentException($"Invalid day '{day}', must be a value from 1 to {this.DaysInSeason}.");
-            if (year < 1)
-                throw new ArgumentException($"Invalid year '{year}', must be at least 1.");
-
-            // initialise
-            this.Day = day;
-            this.Season = season;
-            this.Year = year;
-            this.DayOfWeek = this.GetDayOfWeek();
-        }
+            : this(day, season, year, allowDayZero: false) { }
 
         /// <summary>Get the current in-game date.</summary>
         public static SDate Now()
         {
-            return new SDate(Game1.dayOfMonth, Game1.currentSeason, Game1.year);
+            return new SDate(Game1.dayOfMonth, Game1.currentSeason, Game1.year, allowDayZero: true);
         }
 
         /// <summary>Get a new date with the given number of days added.</summary>
@@ -195,6 +179,42 @@ namespace StardewModdingAPI.Utilities
         /*********
         ** Private methods
         *********/
+        /// <summary>Construct an instance.</summary>
+        /// <param name="day">The day of month.</param>
+        /// <param name="season">The season name.</param>
+        /// <param name="year">The year.</param>
+        /// <param name="allowDayZero">Whether to allow 0 spring Y1 as a valid date.</param>
+        /// <exception cref="ArgumentException">One of the arguments has an invalid value (like day 35).</exception>
+        private SDate(int day, string season, int year, bool allowDayZero)
+        {
+            // validate
+            if (season == null)
+                throw new ArgumentNullException(nameof(season));
+            if (!this.Seasons.Contains(season))
+                throw new ArgumentException($"Unknown season '{season}', must be one of [{string.Join(", ", this.Seasons)}].");
+            if (day < 0 || day > this.DaysInSeason)
+                throw new ArgumentException($"Invalid day '{day}', must be a value from 1 to {this.DaysInSeason}.");
+            if(day == 0 && !(allowDayZero && this.IsDayZero(day, season, year)))
+                throw new ArgumentException($"Invalid day '{day}', must be a value from 1 to {this.DaysInSeason}.");
+            if (year < 1)
+                throw new ArgumentException($"Invalid year '{year}', must be at least 1.");
+
+            // initialise
+            this.Day = day;
+            this.Season = season;
+            this.Year = year;
+            this.DayOfWeek = this.GetDayOfWeek();
+        }
+
+        /// <summary>Get whether a date represents 0 spring Y1, which is the date during the in-game intro.</summary>
+        /// <param name="day">The day of month.</param>
+        /// <param name="season">The season name.</param>
+        /// <param name="year">The year.</param>
+        private bool IsDayZero(int day, string season, int year)
+        {
+            return day == 0 && season == "spring" && year == 1;
+        }
+
         /// <summary>Get the day of week for the current date.</summary>
         private DayOfWeek GetDayOfWeek()
         {