Chronographer helps you track the long-term accuracy of your mechanical watches. Start by adding your watch collection to the app, creating a “card” for each one. 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 graphs and calculate accuracy metrics.
When you launch Chronographer, you’ll see a list of the watches that the app is tracking. Each watch has its own card showing the watch’s name, a picture, and a handful of important metrics:
Deviation—The long-term average (best-fit) number of seconds that the watch has gained or lost each day.
Time Last Set—How long ago the watch’s time was set.
Last Data Point—How long ago 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).
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 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 deviation has been very close to zero. 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 or the deviation is very close to zero.
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 variance and use that information to choose resting positions for your watches. 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.
To add a watch to Chronographer, tap the "+" button. You’ll see the New Watch form, where you can enter the following information:
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.
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.
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.
After you’ve entered a name and any other information, tap the Add 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.
Tap a watch’s card in the Watches list to show its detail view. You’ll see the watch’s description (or name, if you didn’t provide a description), its picture (if you selected one), the data point graph, accuracy metrics, and notes.
The graph shows the watch’s data points arranged in chronological order. The graph can show either the watch’s offset from the correct time or its deviation from the correct rate. In addition to the data points themselves, the graph includes a series of best-fit trend lines. A separate line is drawn for each sequence of data points during which the watch’s time was not set.
Above the graph, there are several controls that affect its contents:
Scale—The timespan for the visible portion of the graph, ranging from one week to one year. Regardless of which scale you choose, you can scroll the graph horizontally to reveal all of the watch’s data points.
Type—Either Offset or Deviation. The offset graph shows the difference between the watch’s indicated time and the correct time at each data point. The deviation graph shows the average number of seconds that the watch gained or lost per day in the period between each pair of data points.
Position—You can restrict the graph 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 graph, Chronographer displays several metrics related to the watch’s accuracy. Different metrics are shown depending on whether Offset or Deviation is selected. The metrics are calculated using only the visible data points. They update automatically as you scroll the graph left and right and as you change the scale and position.
If the graph type is Offset, 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 Deviation—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 Deviation graphs:
Average Deviation—The weighted arithmetic mean of the deviation values.
Fastest Deviation—The deviation during the period when the watch ran the fastest.
Slowest Deviation—The deviation during the period when the watch ran the slowest.
Last Deviation—The most recent deviation.
Deviation Variance—The weighted variance of the deviation values. This is a measure of the variability in the watch’s 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 Deviation Drift—An estimate of the per-day increase or decrease in deviation. This indicates whether the watch is speeding up or slowing down over time. The deviation drift is the slope of the least-squares regression line drawn through the deviation values.
Collect data points to give Chronographer the raw data it needs to create graphs 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 down, etc.) since the previous data point.
To record a data point, tap the Add Data Point button 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 touch and hold the time to show a context menu with a range of times to choose from.
Once you've selected a target time, wait for the time shown on your watch to match that time as closely as possible and tap the blue button. Chronographer displays information about the new data point, including the actual and indicated times, the offset, and the deviation 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 per-day deviation 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 per-day deviation will be off by 48 seconds.
If necessary, also set the following:
Position—If you’d like to use Chronographer to help identify positional variance, 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 down. However, Worn and Winder are also available, in case one of those would be more appropriate. Once you’ve gathered enough data points, use the graph’s Position menu to compare deviation metrics in various positions.
Time Was Set—If you have manually set your watch’s time since the last data point, it is 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 Add button. To discard it, tap Cancel.
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).
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.
Deviation—The watch’s average deviation during that period, expressed as the 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 Done.
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 delate all of that watch’s data points.
Chronographer can export all of the information you've collected about a watch, including a complete history of its data points, 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 Move. 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 Move.
To import a watch, tap the “+” button above the watch list 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. To add the watch, tap the Add button; to discard it, tap Cancel.