Dual plot x-axis

one thought (which may not be great if you have a lot of series to compare, but here goes) would be "normalizing"/aligning the datetime values according to those of one arbitrary "base" series. as shown in the example below:

let T = 
    datatable(value:int, dt:datetime)
    [
        1, datetime(2019-07-18 15:26:01),
        2, datetime(2019-07-18 15:27:01),
        1, datetime(2019-07-18 15:28:01),
        2, datetime(2019-07-18 15:29:01),
        3, datetime(2019-07-18 15:30:01),
        1, datetime(2019-07-18 15:31:01),
        5, datetime(2019-07-18 15:32:01),
        0, datetime(2019-07-18 16:26:01),
        1, datetime(2019-07-18 16:27:01),
        2, datetime(2019-07-18 16:28:01),
        3, datetime(2019-07-18 16:29:01),
        2, datetime(2019-07-18 16:30:01),
        1, datetime(2019-07-18 16:31:01),
        0, datetime(2019-07-18 16:32:01),
    ]
;
let T_base = 
    T
    | where dt between (datetime(2019-07-18 15:00)..1h)
    | project series = "15:00 to 16:00", dt, value
;
let T_other = 
    T
    | where dt between (datetime(2019-07-18 16:00)..1h)
    | project series = "16:00 to 17:00", dt, value
;
let diff = toscalar(T_other | summarize min(dt)) - toscalar(T_base | summarize min(dt));
T_base
| union 
(
    T_other
    | extend dt = dt - diff
)
| render timechart