diff --git a/web/apps/photos/src/components/PhotoList/index.tsx b/web/apps/photos/src/components/PhotoList/index.tsx
index 783c26cbe8..72b15ac75a 100644
--- a/web/apps/photos/src/components/PhotoList/index.tsx
+++ b/web/apps/photos/src/components/PhotoList/index.tsx
@@ -20,7 +20,7 @@ import {
     ListChildComponentProps,
     areEqual,
 } from "react-window";
-import { handleSelectCreator } from "utils/photoFrame";
+import { handleSelectCreatorMulti } from "utils/photoFrame";
 import { PublicCollectionGalleryContext } from "utils/publicCollectionGallery";
 
 export const DATE_CONTAINER_HEIGHT = 48;
@@ -793,7 +793,7 @@ export function PhotoList({
         console.timeEnd("t6");
     }, [galleryContext.selectedFile]);
 
-    const handleSelect = handleSelectCreator(
+    const handleSelect = handleSelectCreatorMulti(
         galleryContext.setSelectedFiles,
         mode,
         galleryContext?.user?.id,
diff --git a/web/apps/photos/src/utils/photoFrame/index.ts b/web/apps/photos/src/utils/photoFrame/index.ts
index 8fdc03622a..06d8d41207 100644
--- a/web/apps/photos/src/utils/photoFrame/index.ts
+++ b/web/apps/photos/src/utils/photoFrame/index.ts
@@ -131,3 +131,128 @@ export const handleSelectCreator =
             };
         });
     };
+
+// TODO: This is a copy of handleSelectCreator, forked to
+// handle multiple selections efficiently ("Select all in a single day"). If
+// the code doesn't diverge, we'll have verbatim duplication.
+export const handleSelectCreatorMulti =
+    (
+        setSelected: SetSelectedState,
+        mode: GalleryBarMode | undefined,
+        userID: number | undefined,
+        activeCollectionID: number,
+        activePersonID: string | undefined,
+    ) =>
+    ({ id, ownerID }: { id: number; ownerID: number }) =>
+    (checked: boolean) => {
+        setSelected((selected) => {
+            if (!mode) {
+                // Retain older behavior for non-gallery call sites.
+                if (selected.collectionID !== activeCollectionID) {
+                    selected = {
+                        ownCount: 0,
+                        count: 0,
+                        collectionID: 0,
+                        context: undefined,
+                    };
+                }
+            } else if (!selected.context) {
+                // Gallery will specify a mode, but a fresh selection starts off
+                // without a context, so fill it in with the current context.
+                selected = {
+                    ...selected,
+                    context:
+                        mode == "people"
+                            ? { mode, personID: activePersonID! }
+                            : {
+                                  mode,
+                                  collectionID: activeCollectionID!,
+                              },
+                };
+            } else {
+                // Both mode and context are defined.
+                if (selected.context.mode != mode) {
+                    // Clear selection if mode has changed.
+                    selected = {
+                        ownCount: 0,
+                        count: 0,
+                        collectionID: 0,
+                        context:
+                            mode == "people"
+                                ? { mode, personID: activePersonID! }
+                                : {
+                                      mode,
+                                      collectionID: activeCollectionID!,
+                                  },
+                    };
+                } else {
+                    if (selected.context?.mode == "people") {
+                        if (selected.context.personID != activePersonID) {
+                            // Clear selection if person has changed.
+                            selected = {
+                                ownCount: 0,
+                                count: 0,
+                                collectionID: 0,
+                                context: {
+                                    mode: selected.context?.mode,
+                                    personID: activePersonID!,
+                                },
+                            };
+                        }
+                    } else {
+                        if (
+                            selected.context.collectionID != activeCollectionID
+                        ) {
+                            // Clear selection if collection has changed.
+                            selected = {
+                                ownCount: 0,
+                                count: 0,
+                                collectionID: 0,
+                                context: {
+                                    mode: selected.context?.mode,
+                                    collectionID: activeCollectionID!,
+                                },
+                            };
+                        }
+                    }
+                }
+            }
+
+            const newContext: SelectionContext | undefined = !mode
+                ? undefined
+                : mode == "people"
+                  ? { mode, personID: activePersonID! }
+                  : { mode, collectionID: activeCollectionID! };
+
+            const handleCounterChange = (count: number) => {
+                if (selected[id] === checked) {
+                    return count;
+                }
+                if (checked) {
+                    return count + 1;
+                } else {
+                    return count - 1;
+                }
+            };
+
+            const handleAllCounterChange = () => {
+                if (ownerID === userID) {
+                    return {
+                        ownCount: handleCounterChange(selected.ownCount),
+                        count: handleCounterChange(selected.count),
+                    };
+                } else {
+                    return {
+                        count: handleCounterChange(selected.count),
+                    };
+                }
+            };
+            return {
+                ...selected,
+                [id]: checked,
+                collectionID: activeCollectionID,
+                context: newContext,
+                ...handleAllCounterChange(),
+            };
+        });
+    };