{{ summaryHeading }}
{{ summaryValue }}

{{ summaryLine }}

Basis{{ basisLabel }} Roster{{ resultsReady ? `${values.roster_count} zones` : '—' }} Work window{{ resultsReady ? `${values.in_window_count}/${values.roster_count}` : '—' }}
The instant stays the same; this controls the headline clock and offset comparison baseline.
One zone per line. Invalid and duplicate entries are reported without hiding the valid roster.
{{ zoneInputStatus }}
Load a practical starter, then edit the roster above.
The calendar invite and handoff matrix use this same instant.
Use 5 to 480 minutes.
minutes
The inclusive start of the normal work window in every destination zone.
Weekends remain identified separately even when the window crosses midnight.
Auto is the neutral display default and does not change the underlying instant.
Hidden is the neutral default; enable seconds when log-level precision is useful.
Cross-timezone sync is the default interpretation of the work-window count.
Keep the handoff title concise and recognizable.
Leave blank for a remote handoff with no location label.
ZoneCurrent timeUTC offsetBasis deltaWork stateCopy
{{ row.label }}{{ row.time }}{{ row.date }}{{ row.offset_label }}{{ row.delta_label }}{{ row.work_state }}
ZoneStartsEndsDate shiftWork stateCopy
{{ row.label }}{{ row.local_date_time }}{{ row.local_end_time }}{{ row.date_shift_label }}{{ row.work_state }}

The chart renderer is unavailable. The same offsets remain available in the world-clock roster.


    

  



                            

                                            

                

            

            

        

    


    


                                    
        
                    

                

                

                    

                                                                                

                                
                                    
                                        Current Time
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                                                                                    Run a two-player chess clock with increment or delay rules, low-time cues, and a move ledger for casual games and timed practice.
                                                                            
                                    
                                
                            

                                                                                

                                
                                    
                                        NTP Offset Log Checker
                                                                                    Review NTP or chrony peer evidence for clock offset and uncertainty with configurable gates for stratum, reach, and source selection.
                                                                            
                                    
                                
                            

                                                                                

                                
                                    
                                        Progressive Muscle Relaxation (PMR) Coach
                                                                                    Build a paced progressive muscle relaxation routine that sequences body regions with tense-and-release timing, comfort reminders, and live cues.
                                                                            
                                    
                                
                            

                                            

                

            

        
            

    

        

  

    
A meeting time is incomplete until the date and time zone are clear. At the same instant, one office may be starting Tuesday, another may still be on Monday, and a third may be outside its agreed work window. Converting only the hour can therefore create a one-day scheduling error even when the arithmetic looks right.


    
Coordinated Universal Time (UTC) provides a shared reference for an instant. Local civil time is the human-facing date and clock label produced by applying a region's offset rules to that instant. A place-based IANA time-zone name such as Europe/London carries historical and daylight-saving rules; a short abbreviation such as CST does not uniquely identify a region.


    
    
      
  • For people: show the local date, local time, and named zone together.
    • 
      
  • For systems: keep UTC or a Unix timestamp as the stable instant.
    • 
      
  • For handoffs: compare the destination's weekday and wall time with an explicitly chosen work window.
    • 
    


    
UTC offsets are date-sensitive. Governments can change daylight-saving rules or standard offsets, and devices receive those changes through time-zone database updates. Two cities with the same offset today may diverge later; the same city may also use a different offset in another season.


    
A work-window match is a scheduling clue, not an availability promise. Holidays, leave, flexible hours, and local policy are outside a clock conversion. Payroll cutoffs, travel departures, legal deadlines, and maintenance windows should be checked against the authority that owns the schedule.

  






  

    
How to Use This Tool:

    
Start from the instant you need to coordinate, then compare it under named regional rules.

    
    
      
  1. Choose Clock basis for the headline clock and offset comparison. Local uses the device zone; UTC uses UTC. This choice does not reinterpret the handoff time.
    2. 
      
  2. Enter one IANA zone per line under World clock zones. Use local for the device zone or UTC for UTC. Invalid and duplicate lines are reported while valid unique zones remain available, up to 12.
    3. 
      
  3. Set Handoff time in the device's local time, choose a duration from 5 to 480 minutes, and enter the weekday Workday start and Workday end.
    4. 
      
  4. Review each destination's local date, offset, and work state. Use the Unix value when an immutable second-level reference is needed, and inspect the UTC calendar text before importing it elsewhere.
    5. 
    

  






  

    
Interpreting Results:

    
Read a destination as a set: named zone, local date, local time, and UTC offset. The offset comparison measures the difference from the selected basis at the current observed instant. A positive delta is ahead of the basis; a negative delta is behind it.

    
The handoff classification uses the destination's local weekday and the start of the proposed meeting. Work hours means that starting wall time falls inside the configured weekday window. Weekend always takes precedence. A date-shift label reports whether the destination's local meeting date is the same as, earlier than, or later than the date entered on the device.

    
The recommendation counts zones whose meeting start falls inside the work window. It does not inspect calendars or confirm attendance. When a zone is rejected, replace abbreviations or city names with a valid IANA name rather than estimating a fixed offset.

  






  

    
Technical Details:

    
World-clock conversion begins with one epoch instant. The browser resolves each IANA zone into local date parts and an offset for that instant, then formats those parts according to the selected clock style. The same process is repeated at the proposed handoff instant because a daylight-saving transition can change an offset between now and the meeting.


    
Lookup Core:

    
Zone names are checked against the browser's time-zone support. Each valid unique zone produces current and meeting observations using its place-based rules. The first 12 valid unique zones are kept; an invalid line is reported without discarding the rest of the roster. The lookup depends on the time-zone data installed with the browser or operating system.


    
Formula Core:

    
The Unix timestamp discards milliseconds and reports whole seconds since the Unix epoch.

    

      
        
          tUnix
          =
          ⌊
          tms1000
          ⌋
        
      
    

    
Offset comparison subtracts the basis offset from the destination offset. Offsets are stored in minutes and divided by 60 for the hour chart.

    

      
        
          Δhours
          =
          
            ozone-obasis
            60
          
        
      
    

    
The handoff end is the entered start plus the selected duration in minutes.

    

      
        
          tend
          =
          tstart
          +
          60000d
        
      
    

    
Here o is a UTC offset in minutes and d is the handoff duration in minutes.


    
Rule Core:

    

      

        
        
          

            Condition
            Classification rule
          

        
        
          

            Saturday or Sunday
            Weekend, regardless of the configured hours.
          

          

            Start is before or equal to end
            Work hours when local minutes are greater than or equal to start and strictly less than end.
          

          

            Start is after end
            The window crosses midnight. Work hours when local minutes are greater than or equal to start or strictly less than end.
          

          

            All other weekday times
            Before work, after work, or outside the overnight window.
          

        
      

    

    
Calendar event text uses UTC start and end fields. Commas, semicolons, backslashes, and line breaks in the title or location are escaped before the event is assembled.

  






  

    
Limitations and Privacy:

    
The current time, zone conversions, handoff checks, and calendar text are produced in the browser. The entered zone list and meeting details are not sent away for calculation.

    
    
      
  • A wrong device clock or device zone makes the local basis and entered handoff instant wrong.
    • 
      
  • Browser time-zone data may lag a recent government rule change.
    • 
      
  • Calendar applications can apply their own import, display, and invitation behavior; inspect the imported event before sending it.
    • 
      
  • The work-window result ignores holidays, leave, and individual schedules.
    • 
    

  






  

    
References: