EHT observing schedules for M 87^* (blue) and its calibrator 3C 279 (orange) on the 2018 April 21 (left panel) and April 25 (right panel) observing days, which began at the end in UTC of April 20 and 24, respectively. Open rectangles represent scans that were scheduled but not observed owing to weather or technical issues. The filled rectangles mark the scans with detections in the final data set. On these two particular days, scan durations are typically 4 to 5 min each for M 87^* and 4 min each for 3C 279, as reflected by the width of each rectangle.