diff --git a/server/services/mailService.ts b/server/services/mailService.ts
index 166a083..0b3fc24 100644
--- a/server/services/mailService.ts
+++ b/server/services/mailService.ts
@@ -76,10 +76,9 @@ async function removePendingMailFromQueue(id: MailId): Promise<void> {
 }
 
 async function incrementFailureCounterForPendingEmail(id: MailId): Promise<void> {
-    const now = moment();
     await db.run(
         'UPDATE email_queue SET failures = failures + 1, modified_at = ? WHERE id = ?',
-        [now.unix(), id],
+        [moment().unix(), id],
     );
 }
 
diff --git a/server/services/monitoringService.ts b/server/services/monitoringService.ts
index 0cd4cda..875bbc5 100644
--- a/server/services/monitoringService.ts
+++ b/server/services/monitoringService.ts
@@ -666,6 +666,10 @@ export async function sendMonitoringMails(): Promise<void> {
     }
 }
 
+function toUnixTimestamp(moment: Moment): UnixTimestampSeconds {
+    return moment.unix() as UnixTimestampSeconds;
+}
+
 export async function deleteOfflineNodes(): Promise<void> {
     Logger
         .tag('nodes', 'delete-offline')
@@ -676,10 +680,10 @@ export async function deleteOfflineNodes(): Promise<void> {
         );
 
     const deleteBefore =
-        moment().subtract(
+        toUnixTimestamp(moment().subtract(
             DELETE_OFFLINE_NODES_AFTER_DURATION.amount,
             DELETE_OFFLINE_NODES_AFTER_DURATION.unit
-        ).unix();
+        ));
 
     await deleteNeverOnlineNodesBefore(deleteBefore);
     await deleteNodesOfflineSinceBefore(deleteBefore);
@@ -689,7 +693,7 @@ async function deleteNeverOnlineNodesBefore(deleteBefore: UnixTimestampSeconds):
     Logger
         .tag('nodes', 'delete-never-online')
         .info(
-            'Deleting nodes that were never online created befor ' +
+            'Deleting nodes that were never online created before ' +
             deleteBefore
         );
 
diff --git a/server/services/nodeService.ts b/server/services/nodeService.ts
index b741009..32a1749 100644
--- a/server/services/nodeService.ts
+++ b/server/services/nodeService.ts
@@ -20,7 +20,9 @@ import {
     NodeStatistics,
     to,
     Token,
+    toUnixTimestampSeconds,
     unhandledEnumField,
+    UnixTimestampMilliseconds,
     UnixTimestampSeconds
 } from "../types";
 import util from "util";
@@ -322,10 +324,14 @@ function setNodeValue(prefix: LINE_PREFIX, node: NodeBuilder, nodeSecrets: NodeS
     }
 }
 
+async function getModifiedAt(file: string): Promise<UnixTimestampSeconds> {
+    const modifiedAtMs = (await fs.lstat(file)).mtimeMs as UnixTimestampMilliseconds;
+    return toUnixTimestampSeconds(modifiedAtMs);
+}
+
 async function parseNodeFile(file: string): Promise<{ node: Node, nodeSecrets: NodeSecrets }> {
     const contents = await fs.readFile(file);
-    const stats = await fs.lstat(file);
-    const modifiedAt = Math.floor(stats.mtimeMs / 1000);
+    const modifiedAt = await getModifiedAt(file);
 
     const lines = contents.toString().split("\n");
 
diff --git a/server/types/shared.ts b/server/types/shared.ts
index 9ddc35f..dae75c2 100644
--- a/server/types/shared.ts
+++ b/server/types/shared.ts
@@ -293,8 +293,12 @@ export type MAC = {
 };
 export const isMAC = toIsNewtype<MAC>(isString);
 
-export type UnixTimestampSeconds = number;
-export type UnixTimestampMilliseconds = number;
+export type UnixTimestampSeconds = number & { readonly __tag: unique symbol };
+export type UnixTimestampMilliseconds = number & { readonly __tag: unique symbol };
+
+export function toUnixTimestampSeconds(ms: UnixTimestampMilliseconds): UnixTimestampSeconds {
+    return Math.floor(ms) as UnixTimestampSeconds;
+}
 
 export type MonitoringToken = {
     value: string;