From 60317d4ef1996d01f8d24d12af37a1e088a0c9f0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ce=CC=81dric=20Boirard?= <cedric@framer.com>
Date: Tue, 4 Feb 2025 10:00:34 +0100
Subject: [PATCH] Use SERIAL_NUMBER for Date parsing
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Signed-off-by: Cédric Boirard <cedric@framer.com>
---
 .../src/pages/MapSheetFields.tsx              |  2 --
 plugins/google-sheets/src/sheets.ts           | 30 +++++++++++++++++--
 2 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/plugins/google-sheets/src/pages/MapSheetFields.tsx b/plugins/google-sheets/src/pages/MapSheetFields.tsx
index 7db40c6e..c72abd8a 100644
--- a/plugins/google-sheets/src/pages/MapSheetFields.tsx
+++ b/plugins/google-sheets/src/pages/MapSheetFields.tsx
@@ -56,8 +56,6 @@ const inferFieldType = (cellValue: CellValue): CollectionFieldType => {
 
         // If the cell value contains a newline, it's probably a formatted text field
         if (cellValueLowered.includes("\n")) return "formattedText"
-        const maybeDate = new Date(cellValueLowered)
-        if (!Number.isNaN(maybeDate.getTime())) return "date"
         if (/^#[0-9a-f]{6}$/.test(cellValueLowered)) return "color"
         if (/<[a-z][\s\S]*>/.test(cellValueLowered)) return "formattedText"
 
diff --git a/plugins/google-sheets/src/sheets.ts b/plugins/google-sheets/src/sheets.ts
index de543f02..dcac3180 100644
--- a/plugins/google-sheets/src/sheets.ts
+++ b/plugins/google-sheets/src/sheets.ts
@@ -167,7 +167,7 @@ function fetchSheet(spreadsheetId: string, sheetTitle: string, range?: string) {
         query: {
             range: range ?? sheetTitle,
             valueRenderOption: "UNFORMATTED_VALUE",
-            dateTimeRenderOption: "FORMATTED_STRING",
+            dateTimeRenderOption: "SERIAL_NUMBER",
         },
     })
 }
@@ -279,6 +279,30 @@ export interface SyncMutationOptions {
     lastSyncedTime: string | null
 }
 
+const BASE_DATE_1900 = new Date(Date.UTC(1899, 11, 30))
+const BASE_DATE_1904 = new Date(Date.UTC(1904, 0, 1))
+const MS_PER_DAY = 24 * 60 * 60 * 1000 // hours * minutes * seconds * milliseconds
+
+/**
+ * Extracts a date from a serial number in Lotus 1-2-3 date representation.
+ */
+function extractDateFromSerialNumber(serialNumber: number) {
+    // Use 1900 system by default, but if date is before 1904,
+    // switch to 1904 system
+    let baseDate = BASE_DATE_1900
+    const date1900 = new Date(BASE_DATE_1900.getTime() + serialNumber * MS_PER_DAY)
+
+    if (date1900 < BASE_DATE_1904) {
+        baseDate = BASE_DATE_1904
+    }
+
+    const wholeDays = Math.floor(serialNumber)
+    const fractionalDay = serialNumber - wholeDays
+    const milliseconds = Math.round(fractionalDay * MS_PER_DAY)
+
+    return new Date(baseDate.getTime() + wholeDays * MS_PER_DAY + milliseconds)
+}
+
 function getFieldValue(fieldType: CollectionFieldType, cellValue: CellValue) {
     switch (fieldType) {
         case "number": {
@@ -293,9 +317,9 @@ function getFieldValue(fieldType: CollectionFieldType, cellValue: CellValue) {
             return CELL_BOOLEAN_VALUES.includes(cellValue)
         }
         case "date": {
-            if (typeof cellValue !== "string") return null
+            if (typeof cellValue !== "number") return null
             try {
-                const date = new Date(Date.parse(cellValue))
+                const date = extractDateFromSerialNumber(cellValue)
                 return date.toISOString()
             } catch {
                 return null