Drying out

frontend/src/components/stats/SessionList.tsx

@@ -2,26 +2,7 @@ import React, { useState } from 'react';
 import { useSessions } from '../../hooks/useSleepSession';
 import { Edit2, Check, X } from 'lucide-react';
 import type { SleepSessionRead } from '../../types';
-
-function formatDateTime(isoString: string): string {
-  const iso = isoString.endsWith('Z') ? isoString : isoString + 'Z';
-  const d = new Date(iso);
-  return d.toLocaleString('sv-SE', {
-    year: 'numeric',
-    month: '2-digit',
-    day: '2-digit',
-    hour: '2-digit',
-    minute: '2-digit',
-    hour12: false
-  }).replace(',', ' ');
-}
-
-function toDatetimeLocal(isoString: string): string {
-  const iso = isoString.endsWith('Z') ? isoString : isoString + 'Z';
-  const d = new Date(iso);
-  const pad = (n: number) => n.toString().padStart(2, '0');
-  return `${d.getFullYear()}-${pad(d.getMonth() + 1)}-${pad(d.getDate())}T${pad(d.getHours())}:${pad(d.getMinutes())}`;
-}
+import { formatDateTime, toLocalDatetimeInputValue, getDurationMinutes } from '../../utils/time';
 
 export function SessionList() {
   const { sessions, isLoading, updateSession } = useSessions();
@@ -50,8 +31,8 @@ export function SessionList() {
 
   const startEditing = (s: SleepSessionRead) => {
     setEditingId(s.id);
-    setEditStart(toDatetimeLocal(s.start_time));
-    setEditEnd(s.end_time ? toDatetimeLocal(s.end_time) : '');
+    setEditStart(toLocalDatetimeInputValue(new Date(s.start_time)));
+    setEditEnd(s.end_time ? toLocalDatetimeInputValue(new Date(s.end_time)) : '');
   };
 
   const handleCancel = () => {
@@ -120,10 +101,11 @@ export function SessionList() {
                 </div>
                 <div className="flex items-center space-x-2">
                   <span className="text-blue-600 font-mono text-sm">
-                    {s.end_time && s.start_time
-                      ? `${Math.round((new Date(s.end_time + 'Z').getTime() - new Date(s.start_time + 'Z').getTime()) / 60000)} min`
-                      : '—'}
-                  </span>
+                                    {s.end_time && s.start_time
+                                      ? `${getDurationMinutes(s.start_time, s.end_time)} min`
+                                      : '—'}
+                                  </span>
+
                   <Edit2 size={14} className="text-gray-400" />
                 </div>
               </div>

frontend/src/components/stats/WakeupPlot.tsx

@@ -1,6 +1,6 @@
 import { useEffect, useState } from 'react';
 import { useStats } from '../../hooks/useStats';
-import { formatMinutesAfter, getToday, getLocalOffsetFromReference, timeToMinutes } from '../../utils/time';
+import { formatMinutesAfter, getToday, getLocalOffsetFromReference } from '../../utils/time';
 import {
   LineChart,
   Line,
@@ -35,16 +35,7 @@ const WakeupPlot: React.FC<WakeupBedtimeProps> = ({ from_date, to_date, wakeup_r
 
       let offsetFromRef = 0;
       if (day.wakeup_minutes !== null) {
-        const refMins = timeToMinutes(wakeup_ref);
-        // If wakeup_minutes is significantly smaller than the reference, 
-        // it's likely already an offset (relative), not absolute minutes from midnight.
-        const isLikelyOffset = day.wakeup_minutes < refMins && day.wakeup_minutes < 120; 
-        
-        if (isLikelyOffset) {
-          offsetFromRef = day.wakeup_minutes;
-        } else {
-          offsetFromRef = day.wakeup_minutes - refMins;
-        }
+        offsetFromRef = getLocalOffsetFromReference(day.wakeup_minutes, wakeup_ref);
       }
 
       return {

frontend/src/components/tracker/TimeAdjuster.tsx

@@ -1,23 +1,11 @@
 import React, { useState, useEffect } from 'react';
+import { toLocalDatetimeInputValue, toUTCFromLocalInput } from '../../utils/time';
 
 interface TimeAdjusterProps {
   onTimeChange: (time: string) => void;
   defaultValue?: string;
 }
 
-function toLocalDatetimeInputValue(date: Date): string {
-  const pad = (n: number) => String(n).padStart(2, '0');
-  return `${date.getFullYear()}-${pad(date.getMonth() + 1)}-${pad(date.getDate())}T${pad(date.getHours())}:${pad(date.getMinutes())}`;
-}
-
-function toUTCFromLocalInput(inputValue: string): string {
-  const [datePart, timePart] = inputValue.split('T');
-  const [year, month, day] = datePart.split('-').map(Number);
-  const [hours, minutes] = timePart.split(':').map(Number);
-  const localDate = new Date(year, month - 1, day, hours, minutes);
-  return localDate.toISOString();
-}
-
 const TimeAdjuster: React.FC<TimeAdjusterProps> = ({ onTimeChange, defaultValue }) => {
   const [value, setValue] = useState(() => {
     if (defaultValue) {