Chronographer helps you track the long-term accuracy of your mechanical watches. Start by adding your collection to the app, creating a “card” for each watch. Then, periodically collect data points, comparing a watch’s indicated time with the current correct time. Chronographer stores this information and uses it to create charts (scatter plots and histograms) that help you visualize your watches’ performance over time, along with detailed metrics related to their overall accuracy.
Chronographer also lets you track how often you wear each of your watches. Log which watch (or watches) you wear each day, and Chronographer can compare wrist time and tell you how long it’s been since you’ve worn each watch.
When you first start using Chronographer, you'll need to create a card for each watch in your collection. To add a watch, tap the + button. You’ll see the New Watch form, where you can enter the following information:
Picture—You can choose a picture from your Photos library to be shown on the watch’s card and in its detail view. For best results, use a picture that has been cropped to a square.
Name—The name to be shown on the watch’s card. This cannot be left blank.
Description—An optional longer description to be used in the watch’s detail view. If you don’t provide a description, the watch’s name will be used there instead.
Notes—Use this field to record the watch’s purchase details, service history, dimensions, movement specifications, or anything else you think is important.
Keep Data Points—Choose whether Chronographer should keep the watch’s data points forever, or whether they should automatically be deleted after 30 days, or after a year. Note that this setting also affects the watch’s history of worn days.
After you’ve entered a name and any other information, tap the checkmark button to create the watch’s card and return to the main watch list. If you ever need to change any of this information, use Edit Watch in the menu in the watch’s detail view. To delete the watch’s card, select Delete Watch from that same menu.
You can also add watches by importing them from iCloud Drive. For more information, see the Exporting & Importing section below.
When you launch Chronographer, you’ll see a list of the watches that the app is tracking. Each watch has its own card showing its name, a picture, and a handful of important metrics:
Average Rate—The average number of seconds that the watch has gained or lost each day (best-fit average over the last 30 days).
Time Last Set—How long it’s been since the watch’s time was set.
Last Data Point—How long it’s been since the most recent data point was recorded.
Last Offset—The number of seconds that the watch was ahead or behind the correct time when the last data point was recorded.
Trend indicator—A symbol indicating whether the watch has recently been gaining or losing time and whether it is converging with, or diverging from, the correct time (see below).
Last Worn—How long it’s been since the watch was last worn.
Watches are listed in alphabetical order. You can search the list by tapping in the search field and typing; only watches with matching names will be shown.
Trend indicators are small symbols shown along with the metrics in a watch’s card, on the same line as the last offset. They combine two pieces of information:
Whether the watch has recently been gaining or losing time. The indicator contains an arrow sloping up if the watch is gaining time, sloping down if it is losing time, and horizontal if the watch’s daily rate has been nearly perfect. If there are not enough data points to establish a trend, the arrow is replaced by an ellipsis.
Whether the watch is trending towards showing the correct time (converging) or away from the correct time (diverging). The indicator is green if the watch is converging, red if it is diverging, and gray if either the offset is near zero or the daily rate is very close to correct.
If you typically set your watches slightly ahead or behind the correct time depending on whether they tend to run slow or fast, trend indicators can help you decide when it’s time to set a watch. Generally, this will be when its offset is higher than you prefer and the indicator is red.
Trend indicators may also be useful if you track positional variation and use that information to choose resting a position for your watches (sometimes called “simple regulation”). If a particular watch runs fast in some positions and slow in others, a red indicator suggests that it may be time to change the watch’s position to one that will cause it to trend back towards the correct time.
Tap a watch’s card in the Watches list to show its detail view. You’ll see:
The watch’s picture (if you selected one).
Its description (or its name, if you didn’t provide a separate description).
Controls that can be used to select the data to be included in the chart and metrics shown below.
A chart—either a scrollable scatter plot or a histogram.
Metrics (see below).
Any notes provided when the watch was added or last edited.
The controls include:
The size of the timespan to be considered, ranging from a week to a year.
Offset/Rate—A watch’s offset is the difference between its indicated time and the correct time at each data point. The rate is the average number of seconds that the watch gained or lost per day in the period between each pair of offsets.
Scatter Plot/Histogram—A scatter plot shows data points (offset or daily rate) arranged in chronological order. It also includes best-fit trend lines, one for each continuous sequence of data points where the watch’s time was not set. Days where the watch was worn are highlighted in blue. You can scroll the scatter plot horizontally to reveal all of the available data points. A histogram shows the distribution of offset or rate values in the selected time period.
Position—You can restrict the scatter plot or histogram to data points that match a specific position. This feature can help you to characterize a watch’s positional variation. Select All Positions to show all data points, regardless of position.
Below the scatter plot or histogram, Chronographer displays several metrics related to the watch’s accuracy. Different metrics are shown depending on whether Offset or Rate is selected. The metrics are calculated using only the visible data points. They update automatically as you scroll the scatter plot left or right, and as you change the scale and position.
If offsets are being displayed, you’ll see the following metrics:
Average Offset—The arithmetic mean of the offsets.
Max. Positive Offset—The largest amount that the watch was ahead of the correct time.
Max. Negative Offset—The largest amount that the watch was behind the correct time.
Last Offset—The most recent offset.
Net Gain/Loss—The amount of time that the watch gained or lost between the first data point and the last.
Best-Fit Rate—An estimate of the number of seconds that the watch gained or lost each day. This is the slope of the least-squares regression line drawn through the offsets.
For rate:
Average Rate—The weighted arithmetic mean of the rate values.
Fastest Rate—The daily rate during the period when the watch ran the fastest.
Slowest Rate—The daily rate during the period when the watch ran the slowest.
Last Rate—The most recent daily rate.
Rate Variance—The weighted variance of the rate values. This is a measure of the variability in the watch’s daily rate. A small value indicates that the watch’s rate was fairly consistent; a large value means that it varied significantly over time.
Best-Fit Rate Drift—An estimate of the per-day increase or decrease in that watch’s rate. This indicates whether the watch is speeding up or slowing down over time. The rate drift is the slope of the least-squares regression line drawn through the rate values.
Collect data points to give Chronographer the raw data it needs to create charts and calculate accuracy metrics. Each data point records the difference between a watch’s indicated time and the correct time. It can also include the watch’s primary or resting position (dial up, crown up, etc.) since the previous data point.
To record a data point, tap the Add Data Point button (pencil and paper icon) at the bottom of a watch’s detail view. Or, you can touch-and-hold a card in the watch list to activate its context menu, and then select Add Data Point. Either of these methods brings up the New Data Point form.
Near the bottom of the form, above the big blue button, you’ll see the target time. You’ll capture a data point by tapping the blue button when the time shown on your watch matches that time.
Chronographer tries to pick a target time that’s a few seconds ahead of the watch’s indicated time. It uses recent data points to predict the watch’s current offset and rounds to a multiple of five seconds. If this estimate is not correct, you can adjust the target time by tapping the + and - buttons. You can also tap the target time to re-calculate the estimate, or you can touch-and-hold the time to show a context menu with a range of times to choose from (this can be useful after you’ve set your watch).
Once you've selected a target time, wait for the time shown on your watch to match that time as closely as possible, and then tap the blue button. Chronographer displays information about the new data point, including the actual and indicated times, the offset, and the daily rate since the previous data point. If you're not happy with the result, you can adjust the target time and try again.
For best results, collect a data point for each watch every day or two. If data points are taken too close together, small inaccuracies can be magnified, causing large errors in the daily rate calculations. For example, if you record two data points fifteen minutes apart, and if you’re just a half-second early or late tapping the blue button, the resulting daily rate will be off by 48 seconds.
If necessary, also set the following:
Position—If you’d like to use Chronographer to help identify positional variation, you can record a position along with each data point. This will typically be the position that the watch was stored in overnight, such as Dial Up or Crown Up. However, Worn and Winder are also available, in case one of those would be more appropriate.
Time Was Set—If you have manually set your watch’s time since the last data point, it’s important to select Time Was Set. This lets Chronographer know not to attribute any change in the offset to the watch running fast or slow during that period.
Once you're satisfied with the new data point, you can permanently record it by tapping the checkmark button. To discard it, tap X.
To see all of the data points that you’ve collected for a watch, tap Show Data Points in the watch’s detail view menu. The data point list shows the time that each data point was recorded along with the corresponding offset. Data points are listed in reverse chronological order, i.e., with the most recent ones at the top of the list. To reverse the order, tap the sort order button (up/down arrows) and select Oldest First.
Tap a data point to see its details:
Indicated time—The time shown on the watch.
Offset—The difference between the indicated time and the correct time.
Position—The watch’s position, or None if you didn’t specify a position.
Time Was Set—Yes if the watch’s time was set; No otherwise.
If there’s a data point preceding the one being shown, and if the watch’s time was not set, then two additional pieces of information are included:
Change—The number of seconds that the watch gained or lost since the previous data point and the elapsed time between the two data points.
Rate—The watch’s rate during that period, expressed as the average number of seconds gained or lost per day.
If you need to change the offset, position, or whether the time was set for an existing data point, tap the Edit button, make the desired changes, and then tap the checkmark.
Use the four navigation buttons (|<, <, >, and >|) to view the watch's first, previous, next, and last data points, respectively.
You can delete data points by swiping left on the corresponding row in the data point list. You can also tap Edit to enter edit mode, where you can delete data points individually or use the Delete All button to delete all of that watch’s data points.
To allow Chronographer to track how often you wear each of your watches, use the Worn Today button (hand icon) at the bottom of the watch detail view (next to the Add Data Point pencil and paper). For simplicity, Chronographer only tracks which watches you’ve worn on any given day—it doesn’t keep track of the exact hours and minutes that each one spends on your wrist. This means that you just need to tap the Worn Today button at some point during the day. It may be convenient to do this when you first put the watch on, but it’s also fine to do it later in the day. There’s no need to do anything when you take the watch off. But, if you wear that same watch again the next day, you’ll need to tap the button again.
If you wear more than one watch over the course of a day, tap the Worn Today button for each one. Chronographer will record the fact that they were all worn that day (although it won’t keep track of the amount of time each of them was worn).
After you tap a watch’s Worn Today button, it stays highlighted for the rest of the day to indicate that the watch is being logged as worn. If you mistakenly tap the button, you can tap it a second time to turn it off. As a shortcut, the context menu that appears when you touch-and-hold a watch’s card in the main list includes a Worn Today item that has the same effect as the button.
To see a bar chart comparing the number of days each watch has been worn, tap the Wrist Time button (hand icon) at the top of the main watch list. The chart initially compares wrist time over the past week, but you can select longer timespans, ranging up to a year.
Each watch’s card in the main list includes the time since it was last worn. In addition, the days a watch was worn are highlighted with a blue background in the scrolling offset/rate scatter plot in its detail view.
The Worn Today button and context menu item affect only the current day. If you need to correct the history for previous days, select Show Worn Days from the menu at the top of a watch’s detail view. You’ll see a list containing all of the worn days recorded for that watch. You can add new days (+ button) and remove previously recorded days (swipe left or use the Edit button) as needed.
Chronographer can export all of the information you've collected about a watch, including a complete history of its data points and worn days, to a file stored either on your device or in iCloud Drive. This can be useful for making backups or for sharing your data with other people. Each export file contains a JSON representation of the information associated with a single watch.
To export a watch, navigate to its detail view and tap Export Watch in the menu. Then, select a folder for the file and tap Save. By default, Chronographer uses the watch’s name for the file name and adds the file type “.json”. If you want to use a different name, replace the default one before tapping Save.
To import a watch, tap the + button to display the New Watch form, and then tap the Import Watch button. Navigate to the folder containing the watch’s file and tap the file. The watch’s name, picture, etc., will be loaded into the Add Watch form. You can change any of this information before adding the watch. Use the Import History toggle to control whether the watch's data points and worn day history are imported. To add the watch, tap the checkmark button; to discard it, tap X.