diff --git a/src/libstore/profiles.cc b/src/libstore/profiles.cc
index 4de4e126d..6bec2e515 100644
--- a/src/libstore/profiles.cc
+++ b/src/libstore/profiles.cc
@@ -139,8 +139,7 @@ void deleteGeneration(const Path & profile, GenerationNumber gen, bool dryRun)
     }
 }
 
-
-void deleteGenerations(const Path & profile, const std::set<GenerationNumber> & gensToDelete, bool dryRun)
+void deleteNumberedGenerations(const Path & profile, const std::set<GenerationNumber> & gensToDelete, bool dryRun)
 {
     PathLocks lock;
     lockProfile(lock, profile);
@@ -249,6 +248,26 @@ time_t parseOlderThanTimeSpec(std::string_view timeSpec)
     return curTime - *days * 24 * 3600;
 }
 
+void deleteUnusedGenerations(const Path & profile, std::string_view period, bool dryRun) {
+    if (period == "old") {
+        deleteOldGenerations(profile, dryRun);
+    } else if (period.find('d') != std::string::npos) {
+        auto t = parseOlderThanTimeSpec(period);
+        deleteGenerationsOlderThan(profile, t, dryRun);
+    } else if (period.find('+') != std::string::npos) {
+        if (period.size() < 2)
+            throw Error("invalid number of generations '%1%'", period);
+        auto str_max = period.substr(1);
+        auto max = string2Int<GenerationNumber>(str_max);
+        if (!max)
+            throw Error("invalid number of generations to keep '%1%'", period);
+        deleteGenerationsGreaterThan(profile, *max, dryRun);
+    } else {
+        throw Error("invalid generation to delete '%1%'", period);
+    }
+}
+
+
 
 void switchLink(Path link, Path target)
 {
diff --git a/src/libstore/profiles.hh b/src/libstore/profiles.hh
index 7e7bbf04d..b322f9402 100644
--- a/src/libstore/profiles.hh
+++ b/src/libstore/profiles.hh
@@ -128,48 +128,23 @@ void deleteGeneration(const Path & profile, GenerationNumber gen, bool dryRun);
  * Trying to delete the currently active generation will fail, and cause
  * no generations to be deleted.
  */
-void deleteGenerations(const Path & profile, const std::set<GenerationNumber> & gensToDelete, bool dryRun);
+void deleteNumberedGenerations(const Path & profile, const std::set<GenerationNumber> & gensToDelete, bool dryRun);
 
 /**
- * Delete generations older than `max` passed the current generation.
+ * Delete unused generations.
  *
  * @param profile The profile, specified by its name and location combined into a path, whose generations we want to delete.
  *
- * @param max How many generations to keep up to the current one. Must
- * be at least 1 so we don't delete the current one.
+ * @param period Specifies which generations to keep.
+ * "old" removes all unused generations.
+ * "+*N*" will keep up to *N* generations older than the current generation.
+ * "*N*d" will keep up to *N* days older than the current generation
  *
  * @param dryRun Log what would be deleted instead of actually doing
  * so.
  */
-void deleteGenerationsGreaterThan(const Path & profile, GenerationNumber max, bool dryRun);
+void deleteUnusedGenerations(const Path & profile, std::string_view period, bool dryRun);
 
-/**
- * Delete all generations other than the current one
- *
- * @param profile The profile, specified by its name and location combined into a path, whose generations we want to delete.
- *
- * @param dryRun Log what would be deleted instead of actually doing
- * so.
- */
-void deleteOldGenerations(const Path & profile, bool dryRun);
-
-/**
- * Delete generations older than `t`, except for the most recent one
- * older than `t`.
- *
- * @param profile The profile, specified by its name and location combined into a path, whose generations we want to delete.
- *
- * @param dryRun Log what would be deleted instead of actually doing
- * so.
- */
-void deleteGenerationsOlderThan(const Path & profile, time_t t, bool dryRun);
-
-/**
- * Parse a temp spec intended for `deleteGenerationsOlderThan()`.
- *
- * Throws an exception if `timeSpec` fails to parse.
- */
-time_t parseOlderThanTimeSpec(std::string_view timeSpec);
 
 /**
  * Smaller wrapper around `replaceSymlink` for replacing the current
diff --git a/src/nix-collect-garbage/nix-collect-garbage.cc b/src/nix-collect-garbage/nix-collect-garbage.cc
index 91209c978..ce35b4aae 100644
--- a/src/nix-collect-garbage/nix-collect-garbage.cc
+++ b/src/nix-collect-garbage/nix-collect-garbage.cc
@@ -13,7 +13,7 @@
 
 using namespace nix;
 
-std::string deleteOlderThan;
+std::string deletePeriod = "old";
 bool dryRun = false;
 
 
@@ -43,11 +43,7 @@ void removeOldGenerations(std::string dir)
             }
             if (link.find("link") != std::string::npos) {
                 printInfo("removing old generations of profile %s", path);
-                if (deleteOlderThan != "") {
-                    auto t = parseOlderThanTimeSpec(deleteOlderThan);
-                    deleteGenerationsOlderThan(path, t, dryRun);
-                } else
-                    deleteOldGenerations(path, dryRun);
+                deleteUnusedGenerations(path, deletePeriod, dryRun);
             }
         } else if (type == std::filesystem::file_type::directory) {
             removeOldGenerations(path);
@@ -70,7 +66,7 @@ static int main_nix_collect_garbage(int argc, char * * argv)
             else if (*arg == "--delete-old" || *arg == "-d") removeOld = true;
             else if (*arg == "--delete-older-than") {
                 removeOld = true;
-                deleteOlderThan = getArg(*arg, arg, end);
+                deletePeriod = getArg(*arg, arg, end);
             }
             else if (*arg == "--dry-run") dryRun = true;
             else if (*arg == "--max-freed")
diff --git a/src/nix-env/nix-env.cc b/src/nix-env/nix-env.cc
index c72378cd5..9fdf27d44 100644
--- a/src/nix-env/nix-env.cc
+++ b/src/nix-env/nix-env.cc
@@ -1366,19 +1366,8 @@ static void opDeleteGenerations(Globals & globals, Strings opFlags, Strings opAr
     if (opFlags.size() > 0)
         throw UsageError("unknown flag '%1%'", opFlags.front());
 
-    if (opArgs.size() == 1 && opArgs.front() == "old") {
-        deleteOldGenerations(globals.profile, globals.dryRun);
-    } else if (opArgs.size() == 1 && opArgs.front().find('d') != std::string::npos) {
-        auto t = parseOlderThanTimeSpec(opArgs.front());
-        deleteGenerationsOlderThan(globals.profile, t, globals.dryRun);
-    } else if (opArgs.size() == 1 && opArgs.front().find('+') != std::string::npos) {
-        if (opArgs.front().size() < 2)
-            throw Error("invalid number of generations '%1%'", opArgs.front());
-        auto str_max = opArgs.front().substr(1);
-        auto max = string2Int<GenerationNumber>(str_max);
-        if (!max)
-            throw Error("invalid number of generations to keep '%1%'", opArgs.front());
-        deleteGenerationsGreaterThan(globals.profile, *max, globals.dryRun);
+    if (opArgs.size() == 1) {
+        deleteUnusedGenerations(globals.profile, opArgs.front(), globals.dryRun);
     } else {
         std::set<GenerationNumber> gens;
         for (auto & i : opArgs) {
@@ -1387,7 +1376,7 @@ static void opDeleteGenerations(Globals & globals, Strings opFlags, Strings opAr
             else
                 throw UsageError("invalid generation number '%1%'", i);
         }
-        deleteGenerations(globals.profile, gens, globals.dryRun);
+        deleteNumberedGenerations(globals.profile, gens, globals.dryRun);
     }
 }
 
diff --git a/src/nix/profile.cc b/src/nix/profile.cc
index c89b8c9bd..eca07b854 100644
--- a/src/nix/profile.cc
+++ b/src/nix/profile.cc
@@ -960,11 +960,8 @@ struct CmdProfileWipeHistory : virtual StoreCommand, MixDefaultProfile, MixDryRu
 
     void run(ref<Store> store) override
     {
-        if (minAge) {
-            auto t = parseOlderThanTimeSpec(*minAge);
-            deleteGenerationsOlderThan(*profile, t, dryRun);
-        } else
-            deleteOldGenerations(*profile, dryRun);
+        auto period = minAge ? *minAge : "old";
+        deleteUnusedGenerations(*profile, period, dryRun);
     }
 };