Documentation says that wrtd_tstamp field for nanoseconds wraps at 1e9: https://wrtd.readthedocs.io/en/latest/usage_clib.html#_CPPv411wrtd_tstamp

In WRTD lib, the wrtd_set_attr_tstamp() should check the provided tstamp and if the ns field is greater than (1e-9)-1, it should increase the seconds field and decrease the ns field, until the structure is compliant.