Add configurable TIMEZONE for web UI display (UTC storage preserved)

server/timezone_utils.py

@@ -0,0 +1,69 @@
+"""Timezone helpers for web UI."""
+from contextvars import ContextVar
+from datetime import datetime
+from typing import Optional
+from zoneinfo import ZoneInfo, ZoneInfoNotFoundError
+
+_current_timezone: ContextVar[str] = ContextVar("current_timezone", default="UTC")
+
+
+def set_current_timezone(tz: str) -> None:
+    _current_timezone.set(tz)
+
+
+def get_current_timezone() -> str:
+    return _current_timezone.get()
+
+
+def get_common_timezones() -> list[str]:
+    """Return a curated list of common IANA timezones for the UI."""
+    return [
+        "UTC",
+        "Europe/Moscow",
+        "Europe/Samara",
+        "Asia/Krasnoyarsk",
+        "Asia/Novosibirsk",
+        "Asia/Irkutsk",
+        "Asia/Yakutsk",
+        "Asia/Vladivostok",
+        "Asia/Kamchatka",
+        "Asia/Almaty",
+        "Asia/Tashkent",
+        "Asia/Tbilisi",
+    ]
+
+
+def _ensure_aware(dt: datetime, default_tz: str = "UTC") -> datetime:
+    if dt.tzinfo is None:
+        return dt.replace(tzinfo=ZoneInfo(default_tz))
+    return dt
+
+
+def localtime(
+    value: Optional[datetime],
+    tz: Optional[str] = None,
+    fmt: str = "%Y-%m-%d %H:%M",
+) -> str:
+    """Convert a UTC datetime to the configured timezone and format it."""
+    if value is None:
+        return "-"
+    tz_name = tz or get_current_timezone()
+    try:
+        zone = ZoneInfo(tz_name)
+    except ZoneInfoNotFoundError:
+        zone = ZoneInfo("UTC")
+    dt = _ensure_aware(value)
+    return dt.astimezone(zone).strftime(fmt)
+
+
+def localtime_iso(value: Optional[datetime], tz: Optional[str] = None) -> str:
+    """Convert a UTC datetime to the configured timezone and return ISO string."""
+    if value is None:
+        return ""
+    tz_name = tz or get_current_timezone()
+    try:
+        zone = ZoneInfo(tz_name)
+    except ZoneInfoNotFoundError:
+        zone = ZoneInfo("UTC")
+    dt = _ensure_aware(value)
+    return dt.astimezone(zone).isoformat()