diff --git a/webapp/src/components/calculations/calculations.test.tsx b/webapp/src/components/calculations/calculations.test.tsx
index b514fdf9c..ddc14fc14 100644
--- a/webapp/src/components/calculations/calculations.test.tsx
+++ b/webapp/src/components/calculations/calculations.test.tsx
@@ -79,6 +79,20 @@ describe('components/calculations/calculation logic', () => {
     card5.fields.properties.property_person = ''
     card5.fields.properties.property_checkbox = ''
 
+    // clone of card 3 but created / updated 1 second later
+    const card6 = TestBlockFactory.createCard(board)
+    card6.createAt = 1625639401000
+    card6.createdBy = 'user_id_2'
+    card6.updateAt = 1625639401000
+    card6.modifiedBy = 'user_id_2'
+
+    // clone of card 3 but created / updated 1 minute later
+    const card7 = TestBlockFactory.createCard(board)
+    card7.createAt = 1625639460000
+    card7.createdBy = 'user_id_2'
+    card7.updateAt = 1625639460000
+    card7.modifiedBy = 'user_id_2'
+
     const cards = [card1, card2, card3, card4]
 
     const properties: Record<string, IPropertyTemplate> = {
@@ -188,6 +202,26 @@ describe('components/calculations/calculation logic', () => {
         })
     })
 
+    test('countUniqueValue for cards created 1 second apart', () => {
+        const result = Calculations.countUniqueValue([card3, card6], properties.createdTime)
+        expect(result).toBe('1')
+    })
+
+    test('countUniqueValue for cards updated 1 second apart', () => {
+        const result = Calculations.countUniqueValue([card3, card6], properties.updatedTime)
+        expect(result).toBe('1')
+    })
+
+    test('countUniqueValue for cards created 1 minute apart', () => {
+        const result = Calculations.countUniqueValue([card3, card7], properties.createdTime)
+        expect(result).toBe('2')
+    })
+
+    test('countUniqueValue for cards updated 1 minute apart', () => {
+        const result = Calculations.countUniqueValue([card3, card7], properties.updatedTime)
+        expect(result).toBe('2')
+    })
+
     test('sum', () => {
         const result = Calculations.sum(cards, properties.number)
         expect(result).toBe('170')
diff --git a/webapp/src/components/calculations/calculations.ts b/webapp/src/components/calculations/calculations.ts
index ebae874e1..5153cb900 100644
--- a/webapp/src/components/calculations/calculations.ts
+++ b/webapp/src/components/calculations/calculations.ts
@@ -18,13 +18,13 @@ function getCardProperty(card: Card, property: IPropertyTemplate): string | stri
         return card.createdBy
     }
     case ('createdTime'): {
-        return card.createAt
+        return fixTimestampToMinutesAccuracy(card.createAt)
     }
     case ('updatedBy'): {
         return card.modifiedBy
     }
     case ('updatedTime'): {
-        return card.updateAt
+        return fixTimestampToMinutesAccuracy(card.updateAt)
     }
     default: {
         return card.fields.properties[property.id]
@@ -32,6 +32,12 @@ function getCardProperty(card: Card, property: IPropertyTemplate): string | stri
     }
 }
 
+function fixTimestampToMinutesAccuracy(timestamp: number) {
+    // For timestamps that are formatted as hour/minute strings on the UI, we throw away the (milli)seconds
+    // so that things like counting unique values work intuitively
+    return timestamp - (timestamp % 60000)
+}
+
 function cardsWithValue(cards: readonly Card[], property: IPropertyTemplate): Card[] {
     return cards.
         filter((card) => Boolean(getCardProperty(card, property)))